Because unlike, say, rocket science, painting, music, or programming, banking is a largely unfulfilling, yet incredibly stressful job. Without the gigantic and absurd financial incentives there's really no reason to get into it.
I went to school in engineering and knew more than a few people who went to Wall Street because of the pay (and social status, since our society worships bankers and the ground upon which they tread). I'm not proud to admit it, but there was schadenfreude when the banking industry collapsed - most of these engineers-gone-Wall-Street are still as of yet unemployed. They spent their time dreaming about big money and not enough on, oh, being capable engineers... so now they're stuck up shit creek.
I went to school in engineering and knew more than a few people who went to Wall Street because of the pay (and social status, since our society worships bankers and the ground upon which they tread). I'm not proud to admit it, but there was schadenfreude when the banking industry collapsed - most of these engineers-gone-Wall-Street are still as of yet unemployed. They spent their time dreaming about big money and not enough on, oh, being capable engineers... so now they're stuck up shit creek.