I'd say it varies. For me it was due to loving the game. I didn't want to coach. But I wanted to remain a part of the game. I played baseball in college. Got hurt as a frosh, and then again as a soph. I was done. I signed up for a sports officiating class, and a Coaching 101 class. Bruce Pearl taught the coaching class, and helped in the Sports officiating class. Anyways, he would have our officiating class work his practices, scrimmages, etc, etc...I worked a few practices and just fell in love with it. It was almost like playing again. The connection with the players, coaches, etc, etc...was a great rush. It was like a drug.......I wanted more. Pearl helped me get into a CBB clinic. Even though I had never even worked a HS game, here I was, an 18 year old kid, at a clinic for CBB officials. I fell in love all over again. I worked HS basketball for about 5 years then some small CBB. But shortly after, enlisted in the Army. When I came home, I immediately got back in the circle. Started working HS ball, but with the connections I had made through Pearl, I quickly began to move up. The rest is history.
I do it because I love the game. I love the atmosphere. The relationships you bukld with players/coaches. And yes----the fans. There is no better rush than walking into an areana with 17,000 folks scraming. Band playing. Man it's awesome.
Oh, and the money. That helps.