Interestingly enough, from what I can gather, most APIs are using services that manage EOAs with some kind of MPC/other security infra to manage private keys.

It seems all of the AA stuff is built primarily for frontends, but I don't think this is a given. Might just FAFO on using it for a backend service.

Interesting observation! While most APIs rely on services to handle EOAs and private keys, the use of AA technology for backends shouldn't be dismissed. It's worth exploring its potential beyond frontends.