Some people care less about End-Game and more about the journey to get there.
I preordered SWTOR. Was I disappointed that I didn't stick it with for years to come? Yeah, I suppose. Did my money go to waste? Hell no, the leveling experience for the first characters is awesome! By far one of my favorite MMO Leveling experiences.
Resuming, in my opinion, Pre-orders are nice.. IF you do some research and you are sure you will like what you'll get. Some beta experience of some sort, for example. If one is pre-ordering out of impulse or based on simply hype, it might backfire on you later on.