As far as the numbers above the qwerty keys, there are two reasons those are there AFAICT:
History (the original typewriters didn't have keypads)
Quickness (eight fingers can be faster than 2-4 at entering numbers)
<rant>
Unfortunately the numbers above the qwerty keys do me no good for quickness since i actually have fewer than 10 fingers, so i agree with you that they're an annoyance :)
</rant>