I would tend to think, that there were too many kids at this party to figure out who could ride and who couldn't. That would take time that maybe they didn't have. I can see it now, a bunch of kids just put on horses and let go, lol. Like bumper cars. And just because you can ride does not mean that the horse would not act up, or someone else run their horse into yours, gosh who knows. There are so many things that could happen in a situation like that. Would be different if you were the only one there.