My cousin got banned and my colleagues got banned few years back. The colleagues were banned because they used a common laptop computer and google terminates any associated accounts if one of them is suspended. I can provide screenshots and assure you that Google terminates because their algorithm determines a person to be risk. Almost always its someone reporting you or some financial issue.

Few years back they banned users who failed to use Google Wallet and had Paypal, they also banned users who sold their dev edition pixel.

Recently they banned youtube users who watched the live stream of Russian invasion. Check the threads here https://www.reddit.com/r/youtube/

They were unbanned after a huge ruckus but thousands of cases which fail to bring any attention are just banned for life and all data (gmail, payment, drive, photos etc) are all gone in the morning.

I don't think it matters who's at fault, I think Google should allow the user to extract all their data even after account termination, would be fine if they charged a reasonable fee even.

And it's not like they don't have the capability: the Google Takeout service packages up substantially all of your data on Google services in an archive for download.

Only if you take it out before your account is locked. When was the last time you ran a backup of your google account?