It's worth doing because it helps to serve as a beacon to others, one that illuminates the right thing to do with respect to cats. Hey, I get it, the adopted cat I share my home with has a spot on the carpet he's been grinding at forever, but I could have given him some alternatives. Also, why would anyone adopt a pet if they weren't willing to accommodate its nature and also provide a long and dignified stable loving life for it? 
I like this movement, and I think it's more than merely symbolic.