"Recycle mode" is intended for devices that people are trading up to newer devices. In return for enabling it, you get a 30% discount on any newer hardware, the idea being that you either ship the item back to them, or take it to an e-waste recycler.
Nobody is forced to do this. You're more than welcome to sell/give/etc your speakers to someone else.
The thing is that e waste recyclers generally try to re sell working electronics and have come out hard against Sonos's recycle mode.
There's a reason why the saying is "reduce, reuse, recycle" in that order.
They also don't verify that you recycled it, practically it only makes sure that the otherwise working speaker is removed from the market so that Sonos isn't competing with itself. I'd imagine that a lot of these just end up in the garbage.
Sorry for the late reply, I agree with the others.
If this truly was an environmental initiative, Sonos would rather take a proof of receipt of you giving your previous speaker to an e-waste recycler or even giving away to some place like Goodwill where it'll get reused.
They could just make sure that you were nice and gave away your device for free and/or charity purposes, instead of bricking it forever.
Nobody is forced to do this. You're more than welcome to sell/give/etc your speakers to someone else.