Why does 4e give a flat cost for attribute increases?

[Bruno]

Originally Posted by Skarg

I can see it's simpler this way, but what were the other reasons for this change?

Simply put, it produced dirty dirty point crocks. The most glaring problem is non-humans - you could have two characters with a ST of 18, but one payed a lot less points for the privilege if he had a racial bonus of +4 and bought up his ST by 4, and the other was just buying from 10.