Being guaranteed to be able to talk to a human would be great, but I just don't see how it can possibly scale to over 1 billion users that aren't paying like gmail has.
Years ago, my brother used to work for XBox Live Tech Support, and he said that easily over half the calls he got were for things that customers could easily self-service, like a password reset. Many tech issues were fixed by the most basic troubleshooting step: Power cycling.
Meanwhile, my uncle works XFinity tech support, and he'll frequently get calls when a website has an outage, not to mention how many non-technical people think any internet-related issue, such as a forgotten Google password, means calling your ISP.
This doesn't even begin to talk about bad actors calling tech support to try to break into someone else's account. Google accounts are high-value targets. Once you've gotten in, there's a really good chance you could easily pivot to all of that person's other accounts.
To handle the call volume that a service like Google would have, if they offered phone tech support, the amount of staff they would need would be in the hundreds of thousands, and so many of the calls they take would be wastes of time. There are a lot of non-technical people that have no idea how things work and basically think that Google IS the Internet.