In ring games if you can get a caller, then all-in with Pocket Aces is just fine... you're getting good odds
for the return you'd get. In a tournament if you need to build a stack fast then it's a decent hand to push in with - but sometimes you want to make a rather smaller raise to get some callers, and to avoid risking all your chips on one hand. It's after the flop that you see the really stupid moves by AA - the particular one being to slow-play pre-flop, get lots of callers, and give people a chance to hit 2 pair cheaply, and then push all-in with just the overpair.
Slow-playing is generally a terrible thing to do with Pocket Aces - because after the flop they're often not the best hand any more when you're against a full table, but against only a couple of callers generally they will be. You want to play them fast, just not necessarily for all your chips. Additionally, the main hands that can call a substantial raise are weaker pocket pairs (which have only 2 cards to improve with), and hands like AK and AQ, which are dominated hands, so against the kinds of hands that are likely to call you you've got a greater advantage than over random hands.