Guarantees you a copy when you want. No risk, no hassle.
That isn't a issue anymore, when is the last time you walked into a game store and they said, "sorry sold out". I have never had that happen. Also the huge market online now is easily accessible. Who runs out of copies these days on games, even major releases.
CE is another thing, but regular copies of games seems pointless. Not that it is a hassle to pre order anything, just never seems to be a great incentive for me to pre-order games. I will usually just wait till it releases and then get it. Like Skyrim, I am waiting until tomorrow after work then go get a pre-paid visa card and get Skyrim on Steam.