Well, i dont know about giving the a.i a drift setup. Or actually, in your options somewhere, there is a box that says "a.i use player setups" or something. Click that, and then put yourself a drift set on.
The comment about a.i being too stupid to drift is....well,stupid.
Sure, they cant react as fast as us, but one time when i was messing with a.i, i hit one of the a.i onto the grass (accident, i swear!) and this caused him to drift. He kept it going, and had good angle too