Why weren't proton torpedoes used against AT-AT's?

Why weren't proton torpedoes used against AT-AT's?
Armor being too strong for blasters is one thing. A proton torpedoe hitting an armored AT-AT. A definate other.

I know that the Air Speeders never had launchers built in them but woudln't a hand held proton launcher be more effective?

 

A ground to At-AT torpedo probably would've worked.. but only if the poor sucker didn't get blown to pieces before he could launch. I mean, you saw how those rebels were just getting mowed down. But that aside, do they really have handheld launchers like that in the SW universe? <_<

Oh, and if Lucas had done that.. The battle wouldn't have been nearly as cool, my 2Â¥.

 

Can't remember where I read this, but I think proton torpedoes are expensive and difficult to come by. That would explain why each ship only had a few in EP4.

 

Ok, depending on how much of the SW universe you take to heart (EU)...here's something interesting from The Essential Guide to Weapons and Technology:

"Same infantry units carry shoulder - or backpack-mounted proton torpedo launchers. While heavy and relatively expensive, they are quite effective in protecting infantry from starfighter attacks."

If they can pick off a starfighter...as long as the money is available, most rebels should be able to hit the broad side of a AT-AT!

And there was that cool ARC trooper in the Clone Wars miniseries who's only job seemed to be walking up with a rocket/Proton Torpedo? launcher and blow something/someone up!