Setting up offlineimap to backup your mail is easy. I run daily backups of my protonmail account so in the even they decide to do something nasty to my account, I wouldn't loose more than a day of mail.
True, and I use offlineimap for a different scenario where I do not have control of the mail server. However, it is still not the same level of control as managing the mail server yourself. I understand why some people don't want to do that, but again, I don't find it to be much trouble at all.