[toast0]

Apps can change behaviors to preserve battery life though. Things like disabling prefetching will likely reduce radio time and thus preserve battery.

Delaying maintenance can help too, and that also helps reduce occurances of power failed during complex data operation and the resulting difficulties of resuming from a partial operation when the state may not have been fully persisted at any point, because filesystems and abrupt power loss don't tend to go so well together.

[nostrademons]

Also things like disabling complex animations, canceling high-CPU background jobs, doing more work on the server side rather than client (trading off latency for battery life), using less complex but less accurate algorithms, etc.

There's a lot of reasons why an app might want to know the battery status, and most of them are for the user's benefit.