going all-in preflop, is a useful tool late-game, when you in a tight spot and praying for a miracle hand anyway. with Aces, Its not that necessary, but with snowmen for instance, you dont want the guy to have a chance at bluffing
you out after the flop. And you dont want him to fold at your small raise after the flop...
Its gambling, true, but sometimes you will be in a position where a "flip of the coin" is favourable. Going all-in pre-flop in early game, is nuts imo, though I would call with aces, if I was reasonably sure to have only one opponent.