Isn’t it just as easy to quickly press the middle button on the rear of the device?

I don’t think I would want my Bluetooth playing audio to stop because I needed to charge the speaker.

A user might forget such a setting and perhaps start wondering why their music stopped playing.

For me, when it's in the dock that means it's inside the house and in range of WiFi, and it's better for battery and better quality to play over wireless. Last night I brought the speaker inside and this morning didn't realize my phone was still connected to it via Bluetooth so accidentally played loud audio over the speaker and woke up my roommate, which was what gave me the idea. I do think it should be an optional setting though, since it's not right for everyone. 

Just to present a very slightly different perspective for consideration here too, the Wife and I like to take advantage of the Move’s portability and when we do get to go away in the campervan, we mostly use the Move on its Bluetooth connection. We would not want to have it auto-switch to WiFi when placed on its charger - it usually stays on Bluetooth all weekend whilst we’re travelling and it can be on/off its charger at various times of the day. 

So the suggestion mentioned, would most-certainly be far better as an ‘optional’ feature in our case.

I also still see the current Bluetooth/WiFi mode switching process as being a simple ‘one button press’ already ...and it may perhaps be a case of some users perhaps thinking to change its mode as the device is returned indoors for use on WiFi, against the likely costs of developing an ‘optional’ auto-switching feature.