Yep, non-turbo AWD cars are few and far between. For some reason, they seem to go hand in hand. [/b]
It's the biggest sanctioning body of them alll.......the marketplace! To gain back all the performance lost in with the addition of AWD, manufacturers add a turbo. I think that in the begining, they found the cars were considered premium models, as they cost more than any similar model, but they were the slowest with no extra luxury touches. So....in order to justify the higher pricing, they added luxury stuff, which made the cars weigh even more, then added turbos to "fix" that problem, and then some!

Tons of exceptions of course, but in general, the AWD models include some form of performance enhancing hardware to gain back performance lost due to the extra weight they carry.