The reason companies sign on to 'joint use agreements' is that the government encourages them to do it overtly and sometimes subtly. As a player in the agreement you get to influence routing, get to have your 'secondary' roads into your property approved at the same time and provide enough justification for the government to allow the road permitting.

A company can't build a trail or road or connect to a road without a permit. So if you don't play fair government isn't going to play nice with you later. For most of the players the saving in being involved in the road far exceed the costs of air freight etc. That said there will always be those that 'game' the system to save a few buck. Those 'gamers' often find that it bites them in the butt later.

As RHammer mentioned the community, hunters, trappers, tourists etc get use the road as part of their governments participation in the road.

... Been There