Some players worry that full respecs will allow powergamers to constantly respec their characters into "whatever is best" at the moment. Here's the thing: powergamers are already playing "whatever is best", and they always will be. The fact of the matter is this: powergamers will always powergame. They will spend hundreds of hours researching and planning their characters, and they will do everything it tanks to twink up and powerlevel their characters. Denying respecs to the entire game will not impact powergamers. They already know exactly which powers they want, which stats to raise, and which advantages to pick.
Respecs are what allow everyone else to be able to enjoy their characters as well. Respecs allow casual players to simply PLAY THE GAME rather than RESEARCH THE GAME. Respecs give regular players the opportunity to tweak and improve their character build so they actually have some hope of competing with the powergamers.
Furthermore, developers almost always find it impossible to resist balancing their game based on the way powergamers play it. Difficulty and xp curves will eventually be tweaked based on how powergamers play. If regular players cannot improve and enhance their builds to keep up, they simply suffer.