Sonos is particularly aggressive with its update policy and the reasons behind this are particularly worrying. As others have stated they don't appear to be for the benefit of customers, but to increase the control and data gathering of the Sonos organisation. Customers are powerless to resist these updates, as the alternative is to lose service; if not immediately then at some point in the future.
The issue first surfaced some time ago when Sonos issued an update that bricked their own controllers. Customers soon found that although the update was supposedly 'optional', in practice it was not. The system constantly prompts if it is not updated, and is vulnerable to anyone using the system triggering an update.
Sonos, like other companies, relies on the fact that its users have a large investment in the system and cannot afford to refuse to go along bu opting out and junking their kit.
Much as I like their hardware I would no longer recommend it.