I am sure they can make an arrow go faster, but its doing so in a way that the arrow can be accurate in the hands of a human, as power is increased, the bows get bogger the strings needed and the size and strength of the arrows
also, as arrows go faster its a lot harder to keep them flying well!
its also a major issue with shooter form, smaller quirks will be huge issues down range I believe!
and to be honest, I think major reason is, its not cost productive to make, and well, not needed to hunt with!