You can enable Advanced Data Protection to address that issue with iMessages.

Giving users an option between both paths is usually best. Most users care a lot more that they can’t restore a usable backup of their messages than they do that their messages are unreadable by the company storing them.

I used to work at a company where our products were built around encryption. Users here on HN are not the norm. You can’t trust that most users will save recovery codes, encryption seed phrases, etc in a manner that will be both available and usable when they need them, and then they tend to care a lot less about the privacy properties that provides and a lot more that they no longer have their messages with {deceased spouse, best friend, business partner, etc}.