If they can be compelled to collect IP addresses - why can't they be compelled to collect your password and revel the contents of any mails the police wants to

If they can be compelled to collect IP addresses - why can't they be compelled to collect your password and revel the contents of any mails the police wants to see? I mean, it's their site and AFAIK there's no way for you to prevent them from accessing the content of your emails, unless they are fully encrypted on the client side - in which case any random mail provider would work the same. From where I stand, the only difference here is that ProtonMail has to receive the warrant before they give up all the info they have on you, and others may do it voluntarily even without that, just to keep on the good side of the police, but since it's not exactly hard to achieve such warrants (and in the US, as we learned, it's ok for the police to lie on such warrants and they know no punishment will come to them even if the lie is discovered later) the difference is minimal. If you have something the police really wants to see, and they can reveal it, they will.