I understand how you can get many like that. I bet most are men who simply talk big and want to show the little lady how manly they are.
It wouldn't bother me whatsoever to have to give a demo of my ability to someone in the trail ride business if I ask for english tack.
We are also very careful when choosing which horses for people to ride. Is based on size, experience, and what the trail and weather are like. We have a few awesome horses for the nervous rider or the beginner and we have a few that more experienced people love yet beginners can handle (all they try to do is eat with beginners). It's definitely sometimes hard to judge this and make it work out perfect, some pairs get along great and some clash.
Simply trying your hardest to please the customers within reason is the best thing to do :) sometimes we even get tipped for doing something to make a persons ride even more enjoyable.