1. Power cuts typically aren't clean off and back-on events — they're often e.g. in storms and involve intermittent losses and/or restorations. I don't really want my devices trying to boot up again every time the power flickers.

2. A number of my devices are on battery backup of some sort — they'll cleanly shut down on low-battery, but turning back on when power is restored is non-trivial in this case.

3. Sometimes a device won't come back cleanly after reboot and will require some manual intervention.