‘Desire paths’ are where people cut off the corners of paths because it is more convenient. If you look in fields near to housing estates you will often find footpaths and bridleways that are more worn than the countryside.
Trails could be created that joined up bits of off-road trail, cycle path, trails through small areas of landscaping on business parks. Most of the infrastructure is there perhaps just needs a few more markers.
Trails traditionally were formed by everyday movements of people or were associated with farming e.g. shepherd trails. These days trails are more often created for recreation. More people now live in cities than in rural areas, so perhaps it makes sense that trails should get formed in and around cities.
There are urban downhill races and road bike races in cities, but what about urban cross country routes, mountain bike style singletrack in a city. They would be cheaper to build, keep people fit and make use of otherwise derelict land. Often in cities there are areas that become wild because they are fenced off or not often used by people. These areas give city dwellers the chance to feel wilderness and nature but in the city.
As cycling grows in popularity the culture also has to grow and it would be great to see an emergence of off-road urban trails for utility purposes.