For me, I made a one off account using my personal email/domain years ago. I think it might have been for a shared link or something. Google required phone numbers so I gave it one. Haven't logged in since and no longer have that phone number.

I got a shared link to an interview assignment during my recent job search, but much to my surprise, Google wouldn't let me login! Password hadn't changed (I use a password manager). However, Google's AI thinks I'm not me. I can answer everything but the phone txt during their recovery process; I even have the original activation email archived so I know the exact date I made the account. I even dusted off my old old old laptop to try using a "recognized device". No luck. All I get are warning emails from Google saying, "Don't worry! We stopped an unrecognized login attempt!"

I asked for access to be given to another email, but I guess I took too long in trying to dig up old hardware and trusting that Google's recovery process was sane. I got rejected.