I think yeah they do it to make sure they made the correct fold. Usually done by people who call too often and are trying to learn to fold good hands

.
Personally I love it when I think for a few seconds after someone bets hard into me, and they show me the nuts... Makes me feel all warm and fuzzy, but I never ask for them to show...
Does anyone predict what the other guy has before folding? It has happened a few times where I have KK and flop/turn is 55aa and they'll check raise me and I'll occasionally say, "555aa?" and then muck. they show I'm right

. I hate it when people always do these predictions tho.
Cheers,
Gutzz