Why can you not set numbers for skill hot keys?

This boggles my mind, I noticed that number keys are not used at all in WC3, and when I tried setting them as skill hot keys for my map, it doesn't let me. What the hell is up with that?

Side number pad is used for items, top row of numbers is used for control groups.

They are used for grouping units, unless I remember wrong.

EDIT: blu is fast.

You should ask Blizzard why, we can't do anything about it. Therefore I will close this.