This is a light weight backpacking forum. With today's light equipment, carrying a pack is not that difficult. I would think pulling a cart over rough and rock trails would take more effort. Few of the trails I have been on are smooth enough or wide enough for a cart.

As for bikes, hikers and bikers usually do not mix well. Hikers have anxiety about being run down and bikers have to watch out so much for hikers that they cannot go as fast as they would like. I would approve of having a few bike-specific trails. Hikers use trails to get somewhere in the wilderness; bikers use trails as the venue for their athletic activity. Yes, they also appreciate the wilderness, but wilderness is down on the list of what makes a good bike trail.