Yes the piano keybed does not support it..

There is only a few keybeds with 88 keys that support aftertouch..
Best of the bunch is YAmaha's Montage 8
Shortly followed by Korgs HD3
and then there is a few Fatar keybeds in several instruments..

This is Rolands high end Piano keybed..
Non of the top knotch piano keybeds supprt aftertouch, as that would probably conflict with being as close to a real grand piano action as possible..

there is one exception.. but thats 20 year old
Thats the kurzweil midiboard..
It was build in corporation with Bob Moog..
And has a real piano mechanic inside..
Weighs a ton tough, definately a studio piece, not a gigging thing

However :



This guy has 2 of them build into his setup
It has poly and mono aftertouch
And every thing can be eddited like aftertouch, velocity, keyrelease trough sliders on the right side of the board. Its nearly impossible to find one tough.