When Association Football (Soccer) was first coded in 1863, the game was strictly amateur. Over the next three decades the game gained in popularity and so did the pressure for Soccer to become a professional sport. Some clubs gave better players illicit payments to retain their services and players were lured from club to club with similar irregular payments. The Football Association came under increasing pressure to eliminate these payments by professionalising the game or risk losing control. In 1895 the Football Association finally relented and allowed payments to players. Today the FA runs both professional and amateur leagues.
Practicing the sport
Of course you can't exclude people from a sport!
Women's soccer become an Olympic sport in 1996.
Athletics is not a professional sport
A professional soccer player is someone who is payed a wage to pley the sport. Effectively someone who plays soccer for a living.