At the foundation of parkour is the development of the ability to move effectively. In a training environment it is perhaps difficult to see the application of the training to real situations, but where you come across situations where movement is necessary the applications become readily apparent.
The most important function of movement comes in situations where you need to escape danger. If you’re trapped in a burning building and can’t use the stairs to escape or are being pursued by a gang armed with knives and baseball bats, you begin to appreciate that having a wider understanding of and capability to move can prove.
In these situations your ability to move becomes the difference between life and death, and the ability to cross difficult terrain will affect your chances of doing anything in the future. The self defence aspect cannot be stressed strongly enough, indeed even martial arts that teach people how to defend themselves against attackers also teach that it is much safer to avoid combat or confrontation.
Another use of movement is in situations where you are attempting to reach a certain place. This can be of just as great an importance as escaping, if for instance, you need to quickly reach a place where medicine is stored, or gain access to a casualty in order to provide medical help.
Although so useful as to be essential in many life-threatening situations, when you consider the combined functions of escape and reach, you cover a huge variety of non-lethal situations as well. An ability to move more effectively can help you in situations that vary greatly in type and importance, from struggling through deep snow to get essential supplies to recovering a kite from a tree or simply trying to get through a crowd to a bus stop before the bus arrives. The more trivial the situation, the less importance an ability to move effectively has and the more difficult the effects are to notice, but the effects are always present.