Basketball is fun to play: Basketball has a very fast and exciting pace of play. Also, each player on the court gets to play both offense and defense and the roles of each player are only loosely defined. Much of basketball easily can be practiced (like shooting or dribbling) with one person making it easy to learn. The sport also is great for one-on-one play all the way up to 5-on-5, so you don't need a big crowd to get a good game going.
Simple equipment: With basketball all you need are a ball and a hoop. Many playgrounds throughout the world have hoops making it easy to get a game going with just a ball.
Basketball is fun to watch: Some of the worlds greatest athletes are basketball players. The game is fast-paced and full of excitement and lots of scoring.
Basketball is an all weather sport: Basketball is often played outside in parks or in driveways, but is also a winter sport played indoors. So you can play basketball year round.