I had exactly one class in college where cheating was rampant. I don't know why, but most of that class cheated on exams; the prof reused exams, and frats had bibles. I didn't see much cheating in my other classes; it was exceptionally rare.

That class was graded on a curve.

I got a 'B', and I would say I was in the 90th percentile for understanding the material. It would have been neigh-impossible to get an 'A' without cheating.