A hobby? I doubt that. I spoke to one official that detailed what they go through on any given night during the week and I sincerely doubt that any of us on here would do this.
A referee in Wayne Co. has a game at Mercer on a Tuesday night with start time of 7:30. That is 1 hr and 40 minutes according to Google. One way! They have to be at the gym at least 45 minutes before start time.
That quickly turns into a 5-to-5.5-hour night for $80. Are you going to do this and listen to a coach or fan cuss you and try to embarrass you? I think not. Also, don't forget the wear and tear on their vehicles and bodies to travel to these games.
I believe that most referees do this as a 2nd job to supplement their incomes and I believe that they all do it because they love the game.