It introduces some pretty important risks of its own though. If you accidentally delete/forget a local private key or lose your primary email domain there is no recourse. It's significantly easier to set up 2FA and account recovery on a third party service
Note that I'm not saying you shouldn't self-host email or anything else. But it's probably more risky for 99% of people compared to just making sure they can recover their accounts.
I have seen much more stories about people losing access to their Gmail because of a comment flagged somewhere else (i.e YouTube) than people losing access to their domains (it is hard to miss all these reminders about renewal and you shouldn't wait until then anyway so that's something under you control).
And good luck getting anyone from Google to solve your problem assuming you get to a human.
Google will never comment on the reasons they disable an account, so all you've read are the unilateral claims of people who may or may not be admitting what they actually did to lose their accounts.
Note that I'm not saying you shouldn't self-host email or anything else. But it's probably more risky for 99% of people compared to just making sure they can recover their accounts.