Three Characters, All the Same Class?

[PerfectH]

I've heard people on this forum and the official WoW Forums say they have things like 3 Warriors, or 4 Hunters, or 3 Mages, etc...

My question is: why? What is the purpose of having more than one character of the same class? The only thing I can think of that would justify this would be:

A.) One for both Alliance and Horde

B.) If you play on multiple servers

C.) Passion for that particular class

But even so, if you really liked the class, why would you make more than one of them? Why not just level the one you have, get it geared well, play it, and enjoy it? Some people like leveling perhaps more than the end-game content, I understand that. I just want some one to explain to me what the purpose is of having multiple characters of the same class.