Simple
Nearly every other major sport requires individual equipment, a specific area to play in, or both.
Golfers need clubs. Lacrosse and hockey players require sticks. Football players need pads and a helmet. Basketball players need a court and hoop.
Soccer requires one ball and a space to play.
Regrettable, you must purchase cleats and shin-guards to play competitively; however, you still require less equipment than other sports, and you can play almost anywhere.