In the olden days (pre-FADEC), the autothrottles had a pretty important task in protecting engine ratings and keeping things like the 'climb' rating during the changing altitude/temperature during a climb.
With the advent of FADEC, that's no longer a significant issue - climb rating occurs at a constant throttle position, and it's pretty hard to have a significant overboost in Normal FADEC mode without really trying.
BTW, the autothrottle on all Boeing airplanes used to be more 'aggressive' in turbulence - it was intentionally slowed down for a number of reasons.