I seem to recall someone once rolled 4d6, dropping the lowest, some rediculous number of times and ended up with an average of 13.333, repeating. This isn't the best way to do it, but the math of statistics in reference to "4d6 drop the lowest" hurts my brain.
For those playing at home, 13.3333 (etc.) minus the 8 point you get as base at point buy is 5.3333 (etc.), which, multiplied by 6 stats, is 32. So, if you believe me about the guy elsewhere on this messageboard somewhere (and believe him about the average), that's the closest point buy to the standard 4d6 drop the lowest method.
Which is all a long way of saying "no."

Mostly as a matter of simplicity- changing now would be a pain. The differences between 30, 32, and 33 are minimal enough to not bother, and you get a slight boost in power from being able to decide which score goes where. I think these are solid arguments for keeping things the way they are.