I have read another post which was closed shortly after I posted. I hope this one can stay civil, this is an interesting topic to me.
After reading all responses, I do believe that there are horses who just have low set heads in their blood. I then looked at a few pictures of horses I know and they have that low head set. So yes, it is in those horses blood.
BUT, I also know that in any competative sport people who are just not that great will do not so great things to try to get ahead. This could include training a horse to hold his head lower then he would normally, or walk far slower then he would prefer. I think if you're going to compete in WP make sure your horses is uited. If he's not, do something he is suited to. Don't force him. It's not fair.
So that's where I am on WP head sets currently, but I always love to hear more.
BTW, isn't it :"Horses for courses" :P