1. Because the Move 2 isn’t designed as a TV speaker. Sonos sells the Ray (optical connection to the TV), the Beam, the Arc, and the Arc Ultra (ARC connection to the TV) as TV speakers. Bluetooth is an input, and as such, is subject to the 75ms delay (mostly buffering, possibly other things) in order to sync across a WiFi signal to other Sonos speakers.
2. Not sure I can answer this question, other than to point at ‘ease of use’ cases with the UI. It certainly would be interesting to know numbers regarding how many are used like this, and how many are used when not ‘plugged in’. But I suspect Sonos ipwont share those numbers. 

Question 1

Move 2 is not designed to be used as a replacement for TV speakers. Consequently, there is no need to include the Home Theatre settings, including that for TV Dialog Sync as an option in the Move 2’s settings. A Bluetooth connection has too large a delay and Sonos is not able to play the audio before it is received.

Question 2

Sonos have stated “Leaving Move 2 on the charging dock long-term will not reduce the battery’s lifespan.”

https://support.sonos.com/en-gb/article/charging-sonos-move-2

1. I agree that MOVE 2 is the wrong product for TV viewing. I suggest that you wait until the Thanksgiving or Christmas recess and reevaluate. This will give your son some time to compare notes with classmates and they can collectively decide what is “best” for this use case.
2. In a bygone era when NiCd batteries ruled in the consumer portable space, due to a design flaw in virtually all products, the battery capacity would decline if always left on the charger. Near the end of mass use of NiCd batteries a new charger strategy was developed to minimize this degradation. Prior to this development we were told to remove the NiCd battery from the charger when fully charged and occasionally we should fully discharge the battery in order to restore full capacity. Lithium ion batteries are almost the exact opposite. They thrive when kept on the charger and degrade when fully discharged — sometimes locking out if discharged too far. If discharged too far the risk of fire increases. This is why the batteries lock out.

Thank you all for your answers.

1. TVs normally have a digital speaker dialog option to speed up or delay the sound output relative to the video display.  Based on the comments, this sounds like the most promising way to try to fix this problem.
2. I did not hear a good reason for why Sonos can’t add their TV Dialog tool to the Move 2.  Allowing users to reduce or adjust buffering based on their use would be helpful. I believe the folks that said the Move 2 isn’t “intended” to be used this way are WRONG. Many TVs have bluetooth and the Move 2 has bluetooth built in. The Move 2 should include controls for the bluetooth that might be useful for users. Historically, Sonos has been wildly successful because its technology is so versatile and provides connectivity across so many different platforms and audio sources. Sonos should keep its devices this way.
3. Sonos 2 suggests having the Move 2 turn itself off to maximize the longevity of the device. Just leaving the Move 2 on its dock is immaterial to my question. I was asking about whether the device can be powered directly from the charging dock without using the battery at all. I didn’t see anyone answer that question. I don’t see an answer from Sonos either. 

Thanks again to all for the help.  

​@Office Drone 

Sorry that you have been less than satisfied with the answers given thus far. We in the community can only comment on what Sonos has provided in writing and/or think intuitively as to what may have been the final thought process. For definitive answers you’d have to contact Sonos directly. Hopefully, the information below will provide a plausible perspective.

Your Statement

• I did not hear a good reason for why Sonos can’t add their TV Dialog tool to the Move 2.  Allowing users to reduce or adjust buffering based on their use would be helpful. I believe the folks that said the Move 2 isn’t “intended” to be used this way are WRONG.

Answer taken from Move 2 FAQ’s. Click Here

In addition to the above there’s a little factor when designing a product called “Price Point”. Meaning after all the bells and whistles are factored in...what can a final product designed for its INTENDED use be sold for without pricing itself out of the market based upon competitive products. In the case of the Move 2 its intended use is PORTABILITY to be used as an outdoor Bluetooth speaker with the capability to join the Sonos network as part of a whole-home system speaker. Much in the same manner as an Era 300, Era 100 and/or Five do for music ONLY. They also are not intended for TV audio. That said...by your want...Sonos should design (or redesign) those speakers to account for TV audio latency. There’s a point when a manufacturer has to outline product differences without each product doing everything the other does in the line-up.  Just because we as consumers may think it easy to make a change to a product design doesn’t mean it’s easily done, nor does it necessarily make good business sense for the manufacturer. 

Your Question:

• I was asking about whether the device can be powered directly from the charging dock without using the battery at all. I didn’t see anyone answer that question. I don’t see an answer from Sonos either.

Answer taken from Move 2 User Guide. Click Here