Unless you live in a place with inherently unreliable power, or are flashing in the middle of a thunderstorm/tornado/hurricane/typhoon/earthquake/etc, Flashing is relatively safe as long as you follow directions.
And those risk could be completely eliminated with a dual bios setup, where even if there WAS a failure, it could fall back on the other bios and still work flawlessly. or even better, let you flash the currently inactive one, and switches that to primary upon successful flash. I think even flashback lets you recover from a corrupted bios, too?
So yes, it circles around back to them being cheap and having problems with their process, because they are cheap.