If you don’t think the feature set is worth the money, don’t buy the product.  There is no moral imperative to include a particular feature. Sonos must have considered the technical and marketing implications - and costs - of incorporating other options.  Whether they have got it right or wrong is something that the market will decide

I wouldn't want to see a portable speaker as a surround speaker, personally speaking. Surrounds are a more permanent thing and there are plenty of options from Sonos to fulfil those requirements.
 

The Sonos Move does support dual-stream Bluetooth playback of audio from some top-end android devices and supported transmitters  (eg. https://www.amazon.co.uk/gp/product/B07J58KY3X) and that is good enough for use outdoors/in remote locations. Our garden area is covered by a decent WiFi signal and so I do have the luxury of stereo pairing them outdoors. I’m sure the same could be achieved in some locations with a MiFi hotspot device anyway.

I don’t think either one of these features are an easy flip of the switch type of deal.  From a technical standpoint, the Move is designed for a wide field of audio, which is not what surround speakers do.  The probably could  As well, the Move connects directly to your WiFi network, it does not use the Sonos own network at all, which Sonos uses for home theatre network connectivity.  That was by design so that the Move could be moved around the home  without causing network issues for your other Sonos devices.  In other words, it may seem easy on the surface, but it’s really messy when you start looking at the details.

The other part of this is that cost wise, it doesn’t make a ton of sense. 2 Moves would be $800.  1 Move and 2 Sonos One SLs is $750.   The second scenario gives you the surround sound you’re looking for while having a Move in another room or as a BT speaker without messing with your home theatre setup.

Regarding using 2 Moves as a BT stereo pair, that seems like it would be less complicated. I would guess that Sonos marketing determined that BT stereo pair isn’t used very much outside of the home, and it might cause people to think you need a pair of the speakers for them to sound good.    Personally, I haven’t felt the need to get a 2nd Move.  It’s more than enough for the room it normally sits in and I haven’t wished I could  take two moves with me when I leave the house.