On multi-engine aircraft, it's been pretty much dictated by the regulators that 'fail-safe' is idle (or shutdown), not full power. On the ground, an engine runaway is considered catastrophic - unless the crew shuts down the engine almost immediately, you're going off the runway/taxiway or running into something and the feds consider that potentially catastrophic. A controlled shutdown or fail to idle on a single engine is seldom considered worse than "major" (and never supposed to be worse than 'hazardous') so all newer designs fail-safe to idle or off.
Granted a single engine aircraft is a different story...