[StogeyMike]

I've noticed it, too, and I have even engaged in that practice from time to time. The reason for this is that I have also noticed that standard raising at this stage of a tournament often wins me the blinds only - I seldom get the action that I want with my AA, KK, AK hands.

The play always seems very tight at this stage, with the action being either "fold to the button, raise, win the blinds" or "all-in". It seems rare to see a flop and even rarer to see a showdown. Limping with big hands conveys weakness and sets a trap for someone either stealing or asserting themselves.

Anyway, yes I've noticed the same thing you have and I think the reason for it is to trap/get action on the big hands.