I don't have any strong view whether they should or not. When I worked in a park we did the same and were excited to do so - especially when guests commented on it. It was much cooler and more fun to do it yourself than to turn up in the morning and see what had been dumped on 'your' ride by corporate. I am not sure going the extra mile in your professional life is a bad thing, really. I work more hours than I am paid for, buy refreshments for meetings, buy Christmas decorations, get employee of the month swag out of my own pocket, etc. That's how the world works, in my experience.