For all the haters: actually, it's tricky technology and even Sonos struggles to change volume simultaneously when you have 4+ speakers. WiFi is a big pain.
(That said, Sonos UI is unnecessarily bad, they have terrible support for playing local files and as a consumer I want more competition)
Google made a workaround that uses a different technology. And Sonos still got it blocked.
'When news of the patent decision broke, Google told The Verge it had gotten non-infringing designs approved by the ITC. Sonos warned, however, that Google might have to “degrade or eliminate product features” to be compliant, and that certainly seems to be what’s happening. '
The 2 patents (10,848,885 and 10,469,966) aren't about the technicalities of changing volume simultaneously, they are about the way the zone profiles are updated, configured, and stored so you can refer to them as groups to perform the action on in the first place. From an implementation perspective, the only thing in question here is needing to signal you want to send the volume change control to each device instead of ones in the bedroom. It's unrelated to how you accomplish implementing the change, close in time, across the devices (which are already streaming the music close in time anyways).
I feel like it's just in an unfortunate valley of being slightly too techy, not quite old fashioned enough (e.g. if its that bad I'd add a backup radio), and too expensive (the most prolific user of Sonos products I've met bought probably 15 of them and would've had no qualms spending hundreds on the one that just outputs a signal with no speaker) for there to be much pressure to get it right architecturally.
(That said, Sonos UI is unnecessarily bad, they have terrible support for playing local files and as a consumer I want more competition)