iCloud backups are encrypted, just not end to end. Which is as good as not encrypted.
And you can of course always chose to run local, encrypted backups.
On the other hand, if your adversary wants to get your stuff, they will find a way. The whole cryptography thing is just imposing cost on a potential attacker, not a universal warranty against any possible attack. Someone can still locate you and beat you with XKCD's $5 wrench for your password.
Ideally we'd have end-to-end encryption on everything without adding complexity for end-users. But a lot of that stuff seems to be hard to build and at least just as hard to retroactively bolt on to a system. iMessage (iChat) goes back a long time and supports many platforms (yes, within the apple ecosystem, that is) which means they can't easily nuke every legacy API at once.
This is true, and to add to it: for state level actors, “wanting to get your stuff” expands to passive collection of data as well as well trodden paths to more targeted surveillance. End to end at least throws up a few more barriers.