I always wondered if it's still alive only because Larry or Sergey use it every day.

I think it only survives because it's so thoroughly overlooked. Probably nobody working on a new messaging/chat/VoIP/video conference/etc. platform within Google wants to nominate Google Voice as the thing they're replacing or reinventing.

I hope it stays that way. I'm almost certain that the minute management remembers it's there, it will get shut down, at least for non-paid (i.e. GSuite) accounts.

My hunch is that google uses it for something internally or there's some random government agency that uses it so Google can't quite retire it yet.

Or Gvoice is some backbone service that something else uses. Idk, but it has to be used for something for Google to have not killed it yet.