It's generally desired to put up as few artificial features as possible to maintain the natural look of the park. Sometimes it is necessary, of course. The oth

It's generally desired to put up as few artificial features as possible to maintain the natural look of the park. Sometimes it is necessary, of course. The other problem is that many trails are just maintained by a couple of volunteers. Many in the US are done by local mountain biking clubs, for example. It can be hard enough to maintain what is already there when you're relying on the goodwill of a couple volunteers to do heavy labor at 6am on a Sunday.