Well everyone votes with their wallet differently and businesses only support altcoins because someone is voting differently to you, they do it because it generates a return, its not like these are non-sensical people, they have bills to pay and staff salaries to deal with, telling a business to cut a revenue stream without offering an alternative is kind of pointless

If Bitcoin holders are not spending enough or focusing on bitcoin only isn't viable for them they're not going to do it, and if there is a market for bitcoin only someone else or even you could start it and exploit this under-serviced market if there is revenue to be made