Banks verify your identity when you open your account, which they can refer to later on. Gmail does not, so any “proof of ownership” you can provide is circumstantial.

Banking is a heavily-regulated industry. Their regulators can (& have) seized & shut down a fair number of banks. And the Rich & Powerful would react very badly to any "a bank can lock you out of your money..." precedents.

Basically (& sadly), you're comparing blueberry waffles to the moon. I blame the English usage of "account" for both situations, even though there's very little similarity between a bank "account" and a Gmail "account".

The answer is for Google to be better regulated

Okay. Is there any even-remotely-plausible prospect of that happening in the foreseeable future?

Or is this situation basically "there should be a cure for cancer...but since there is not, here are a whole bunch of laborious things which you need to seriously consider doing, to reduce your risk of dying from cancer..."?

Regulating Google is indeed as hard as curing cancer

Yep. I got locked out of my eBay and GitHub accounts for two different reasons, but through their human support I was able to recover the accounts.