This is incorrect. S1 systems are compatible with Google voice and Alexa, but not Sonos Voice Control.  There are several sonos speakers that have Alexa and Google voice built in.  You can buy a new sonos one, for example, and downgrade it to S1.

This is what the privacy statement says.

How We May Share Personal Information

Sonos does not and will not sell personal information about our customers. However, certain data practices described throughout this Privacy Statement may constitute a “sale” or “sharing” of data under California and/or other US state laws. See the below CA Addendum for more information applicable to CA residents. We want you to understand that information about our customers is an important part of our business. We only disclose your data as described in this Statement. We may share information with the following types of third parties.

I don’t know where you are getting your information, but you couldn’t be more wrong if you tried.  Virtually every statement in your post is the opposite of the truth.

I care about privacy, so i don’t want to use Google/Alexa services. And there is no real technical reason why Sonos Voice Control can’t work with S1, it’s a marketing choice.

> How We May Share Personal Information 

• “may constitute a “sale” or “sharing” of data”.

• “We may share”

Kind of blurry don’t you think ?

Available memory space to run SVC in S1? There certainly isn’t enough to add SMB versions beyond SMB v1, not sure why you’d think there was enough memory / CPU available to add Sonos Voice Control. Not really convinced that’s a ‘marketing choice’ at all. 

Many of the devices that work in the S1 system do not meet the hardware requirements for SVC, among other features that are available only on S2.  Maybe they could get it to work on some speakers, but not all, and without some of the other features, but it would be rather complex to develop and maintain. As well, it makes no sense for Sonos to spend development efforts on a system that isn’t supported by any new product sales.  Call it ‘marketing choice’ if you want, but it makes perfect sense for Sonos to spend development efforts on S2 only.

If the text I quoted was the entire privacy statement, perhaps, but follow the link to see more details and clear up anything you’re unsure about.  If you’re still not happy, then call Sonos for more details or decide you don’t want a Sonos account anymore. 

You could argue that the devices that don’t have enough memory also don’t have mics on board, and would not need the memory for SVC.  They just would need to receive SVC commands from other speakers in the system that are SVC capable.  Probably true.  However, I think it would be extremely difficult to separate the SVC feature from every other feature that is in S2, but S1 isn’t capable of.  It’s arguably the entire reason S2 was created to begin with.  Nor are development efforts to support S1 justified through sale of current S2 speakers. 

I just don’t perceive any logic in the OP’s stance, just bitterness and un-researched complaints, without merit or rigorous thought. 

Then could you please explain why a S2 speaker with full power can’t send simple commands to a S1 group after being controled by voice ? Because it’s already possible with a Mini Google Home. So if Google can do it, Sonos can do it too.

Please. Do we really need to go over again the logic of the S1/S2 split, and why the systems can’t interact? We did that so many times, years ago. There are interminable threads on the subject. 

 Different Sonos systems don’t talk to each other.  They never have.  In order for such a feature to work, the two systems have to be aware and integrated somehow to the point where they know the rooms and music services contained in the other system, be on the exact same network, etc.   Even if that were possible, and maybe it is, the amount of development work to create and test a feature, knowing that it would only be useful to customers with both S1 and S2 who want voice control but not Alexa or Google and are ok with no voice on their S1 speakers, etc, surely doesn’t make any sense.  Not to mention that those same customers will likely not be satisfied with just that, and start claiming they are going to go tell their friends how horrible Sonos is.  Doesn’t really make a whole lot of sense.

Remember too, Sonos goal isn’t to keep S1 around as long as possible, but to incentivize people to fully upgrade to S2 as soon as possible.  This is one of the reasons why they offer discounts to customers with legacy equipment. 

It’s been 3 years.  If you haven’t read the answers as to why it isn’t possible by now, I’m not going to waste my time repeating it.  Suffice to say it’s not possible, regardless of what Google can do.  Time to let it go.  

> Different Sonos systems don’t talk to each other.  They never have.

Again, if Google can talk to my Sonos system, it must not be so impossible. I don’t even ask for the complete package, just need to launch a playlist by voice and select the area.

> It’s been 3 years ...] Time to let it go

Don’t worry, i am let it go, i will not buy anymore Sonos products. Why am i so angry ? Because i love my S1, i use them everyday, they are reliable, but i don’t have any money to upgrade everything. I hate the idea of replacing something that work. When you design products that can last a very long time, you must think about consequences.

Stop it with the Google can do it nonsense.  They are two completely different scenarios.

We think of audio and video equipment as “buy once and use forever” and up into to the 1980’s this was pretty much the case (ignoring the introduction of stereo LP’s, stereo FM, and stereo AM), but then new audio and video formats were introduced at an ever increasing pace. At one point you could buy a “does everything” A/V receiver and it probably still works, but it does not have any HDMI connections. Then it was replaced with an HDMI capable model, but then 4K, 8K, and HDMI-ARC, HDMI-eARC, CEC, Atmos, and many more little nags (such as Bluetooth and AirPlay) were added. 10K and possibly 12K are waiting in the wings. I had to recycle a perfectly functional cellphone because the cell towers stopped supporting it.

I share a lot of your frustration, but we’ve backed ourselves into an impractical corner. We are expecting buy once, free support forever. Unfortunately, this is an impossible business model. The company ends up spending so many resources on free support that it falls behind in creating the new features required to encourage new sales. SONOS almost missed the voice control wagon.

 Sigh. Google connects to Sonos through the cloud, which should bring back that privacy concern you said was the reason you didn't want to use Google in the first place. And, it does not connect to more than 1 Sonos system.

And it's certainly possible, but totally not practical for the reasons I already stated but you chose to ignore. 

But you add to the conversation..instead of just ignoring it..

Some posts don’t provide any value whatsoever.

@ratty has helped tens of thousands of users over the years, I think we can forgive him the occasional comment on the less than earnest effort one has given in researching a long settled issue.  You on the other hand?  I see a lot of complaining, not much helping.  Physician, heal thyself.