Num Lock is all the way over there, do you think I have the energy to move my entire arm that far? I've had auto-run bound to Q since EverQuest.

Caps Lock, on the other hand, is often the run/walk toggle in stealthier FPS games. Much easier than holding down shift for extended periods of time.

Finally, if you want to make Escape and Delete easier to hit, make the keyboard larger so you can place them in the correct locations. Making them bigger isn't going to stop me from having to hunt them down if they're 3" away from where they should be.