Thanks for the insider perspective.
I used Hangouts for a while and had a bunch of contacts on it when it was Android's default SMS app. Many of them were not particularly technical, including one of my parents whom I don't recall telling to use it. If you were using an Android phone, you were probably already logged in to a Google account. iPhone users had to work a little harder for it (install the app and remember the password to the Gmail account they probably already had).
I don't recall the UX on the mobile client having extra complexity over other messaging apps if I didn't go digging in the settings, but it's been a while.
I think the concept of a user having an existing Gmail account if they aren't in the Google ecosystem is a bit of hubris.
There are many people I run across who bypassed the whole Gmail and Google Workspace ecosystems and have rolled along merrily with me.com and other email providers.
It's not a given that users will have bothered to register for a Google account unless they grew up in the Bay Area after a certain time period.
Wind back the clock to when Google tried to roll out Hangouts and the Gmail penetration rate was even lower among the non-Android users out there.
> If you were using an Android phone, you were probably already logged in to a Google account.
Sure. But is it the same Google account that your relatives email you on, or a different one that only that phone is using? When you drop this phone are you going to sign into that same Google account or make a new one? The answers for non-technical users are non-obvious.
A lot of people have a google account because it is created when they setup the smartphone or enter the playstore for the first time for the first time but don't even realize it is not only a "smartphone account" and it gives them access to google workspace/gmail.