For one, Proton can't inspect your content (at rest) for TOS violations. And as a smaller company, they 1) can't afford to lock accounts in as sloppy an automated fashion as MS and Google are known to, and 2) have actual humans working support.
Proton cannot access my content. Go look for cases where people are shut out of their accounts and not being able to get in.
Not sure why the downvote but hey, give me some more for sharing my motivation and experience.