The concept of amateurism in sports took root in the late 1800s, mostly among the wealthy elite of England who spent their weekends competing in various games.
At the time, the working man had limited access to such pursuits. They toiled six days a week in factories or farms owned by the sporting upper class. For them, there was no time for games, let alone the time or energy to master them.
Somewhere along the way, in an effort to influence the outcome of a rugby match or dressage competition, some rich guy decided to pay one of his workers to train for competition rather than perform manual labor.