Background support for non-Apple apps is best-effort at best, and explicitly discouraged in the docs. The rate of silent push notifications and other background mechanisms are intentionally not documented and you’re explicitly instructed you not to rely on any current behavior. They make some exceptions to support money makers like Uber and fitness tracking but generally they don’t like you using anything in the background.
Android is more relaxed but the vendors (like Samsung etc) will go around that and implement their own aggressive background killing bots. Sometimes, this causes alarm apps to stop and not wake you up etc.
The main reason is battery life. Tragically, this makes sense due to the cesspool of spam apps that plague their ”curated” app stores. If you’re an app developer who want to use it responsibly you’re in for a world of trouble. I know because I am one of them (well, I consider myself responsible at least).
The Nextcloud app has been running and syncing in the background on 3 iPhones for like 6 months, so they managed to make that work relatively well.
My issue is other bugs that make it painful, including the fact that I cannot trust that Nextcloud will eventually upload the whole photo gallery (it seems like some files regularly get "locked" w.r.t. "webdav", for some reason, and this never resolves).
Android is more relaxed but the vendors (like Samsung etc) will go around that and implement their own aggressive background killing bots. Sometimes, this causes alarm apps to stop and not wake you up etc.
The main reason is battery life. Tragically, this makes sense due to the cesspool of spam apps that plague their ”curated” app stores. If you’re an app developer who want to use it responsibly you’re in for a world of trouble. I know because I am one of them (well, I consider myself responsible at least).