I know I would be interested in that demo...and the reducing without waste demo too. I suspect Anita is right about the scheduling thing. Might your location have been less than ideal? Was it clearly marked so people could see what was being demoed? I once went to a fiber festival (I am a spinner too) and nearly missed a demo I was dying to see because it wasn't real obvious that that was the place!
At any rate, you have amazing talent and knowledge to share. Since you can't really know if your demo (or anyone else's) will be well attended you will probably have to decide if it is worth it to you. If you will be devastated should you have a repeat, well...it probably wouldn't be worth it to me in that case. Life is just too short to risk feeling that bad, IMO. But if you feel ok with just rolling with whatever happens...then do it! Nothing ventured, nothing gained and all that!