It's all down to the sound generator at the other end of the MIDI cable though. Electric piano's are pretty amazing sounding these days. Lots of music creation software uses sampled, live instruments and some of those are recorded at very high quality. All of which can be driven through MIDI too, although there are obvious limitations to the way a professional can play a real piano, most people would be hard-pressed to tell the difference in a blind test.
Awesome indeed!
I once watched a percussion solo that consisted of a drummer very carefully crumpling a sheet of cellophane. It was beautiful, musical and moving (albeit not very loud). Using things that are not "instruments" as instruments is pretty common among percussionists, and sometimes melodic musicians as well.