Quite frankly, the only purpose for an alt that I can think of would be RP. That doesn't necessarily mean literal roleplaying. For example, it can mean when you feel like playing a Lalafell instead of a Roegadyn one day or you only want to play STR-based classes as one character and INT-based classes on another. But in the end, the game does absolutely nothing to support alts unlike WoW because you can be literally every single class on one character.