I play in 4-5 scrambles a year with friends. It's mainly an excuse to go out, drink some beer, have a good time, and not take golf so seriously. I don't doubt cheating happens, but we're not very good and we know we're not going to win so oh well, whatever makes them feel better.
I've always wondered why scrambles don't use two groups on the same hole instead of one. Would take away a lot of the cheating that happens.