Well, at least with friction bar ends, you know they're probably paying attention to what their doing.

I don't know about other places, but around here,
it seems like the rider's brain often shuts down on the aero bars.

They seem oblivious to the road, other bikes, cars, you name it.
They wreck spectacularly, and fairly often.
I know it must hurt, but it's kind of funny, too.
We call it "racing to the scene of your next wipeout."