Well here's a thing... there's definitely merit to what others say on having role flexibility. And maintaining an alt is a pain: You have to unlock everything twice, sometimes you have to gear twice, etc etc. If you think managing more than one job on a single character is a pain... it's much worse with an alt.

On the other hand... sometimes it is nice to have a getaway character. Or, some very hardcore people will actually raid on more than one character to get around the weekly lockout.