Whilst I can't speak for most other countries (although as the RadioTuner and Radio app both show, globally hundreds of radio stations are totally free-to-air) here in the UK we are more that catered for with regards radio (the mandatory licence fee for the British Broadcasting Corporation covers at least 6 national Radio stations as well as dozens of local/regional stations) and so I couldn't see any reason for Sonos HD Radio subscription - but what about a Premium App subscription?
In light of the problems we're all too aware of I could definitely see the demand for such a app - I know I'd pay for such, if it were an equivalent cost (£5/$7.50 per month type cost). I would like Library management for every subscription service, the return of Music Library for the local network (both of the above, ironically, appear to have returned with the latest update - but let's not kid ourselves, they're intermittently functional at best), the loss of "retired" apps I want brought back - half the reason I maintained an Audiobooks subscription was for Sonos playback, that one in particular was infuriating to have taken away without warning - I'm sure many other features could be brainstormed by more imaginative people than me. Perhaps a playlist curation/creation service, based on listening history; other features that have been considered or even implemented in the past but were too costly or otherwise difficult to maintain, that sort of thing.
Thoughts? I know people probably take that aspect for granted, but as the complexity increases and functionality sacrifices - especially the retiring of services/features etc - are made, wouldn't you rather have the ability to maintain full usage? As I say, I know I would. It could also help with maintaining service availability in the future - Generation 1 has been retired, personally not a problem as I had no Gen1 devices, but as and when Gen 2 retirement arrives...yeah, that'd be a problem, and one I'd certainly rather pay for a premium Sonos app subscription to avoid.
TL;DR
Why don’t Sonos introduce a Support or Premium Support App as a subscription, which unlocks additional features/retains old features, subsidising future updates for general usage? I would much rather pay for such a service and enjoy assurances of such, than gambling with the lottery of future updates.