In all seriousness, though: if I were a user of Google Voice, I'd be seriously concerned that they would shut it down in a way that caused me to lose access to my phone number (even if only indirectly, as happened recently with their divesture of Google Domains or whatever their registrar was called)... you are much braver than I ;P.
Dialects are always in flux and there are plenty of languages out there they haven't conquered, so ... I'd guess they're just leaving it running to detect new speech or languages or dialets or ... personal data gathering or... ?
The speech patterns also differ heavily, with Youtubers (usually) talking in a presentative manner and speaking very clearly.
I think the way people talk in private phone calls, as well as the call audio quality, are much more similar to that of someone speaking to an assistant.
In fact, Google Voice on Android was supposed to make calls via data-only (no minutes usage) on a smartphone, but carriers would not allow Google to do that. Hence the strange random-number dialing which utilizes a 3 way call to make a 2 way call by default. Years later, they quietly allowed calls over data but by then GV was already on lifesupport.
Like Google Domains?
It would also be pretty shortsighted from a business perspective, IMO. Voice could still be extended to compete with iMessage and WhatsApp, like they sort of tried to do back when they were going to merge it with Hangouts.
God please no more messaging apps from Google for the love of god.
I do miss when GV and SMS were integrated with Hangouts though... was imo a much better experience than you get today with all the broken out apps.
The only reason that merger was even allowed to happen was because it was extremely clear that Sprint would not have been a going concern into the next year if it would stay independent.
I feel like Sprint failing may have been better for the market; I expect more Sprint customers would have switched to AT&T or Verizon than to T-Mobile, and T-Mobile would still have to fight for customers.
Instead, T-Mo has jacked up prices just like everyone else, reduced nice perks, and their "uncarrier" movement is but a memory.