My answer to your question, When I left school I did my apprenticeship as a furniture maker and studied at the London College of Furniture, when I qualified I could not get out of the dust quick enough, I moved in to sales and from there set up my own company and employed people, I'm now 55, I walk, (did the tree peaks 2012) play golf, fish follow football there are may other things that I have tried.
Each year my wife buy's me an experience for my birthday and last year it was a two day wood turning course which I went on back in November , I fell in love with it as the first shavings rolled off the gouge. I set up a workshop and started turning the Sunday after Christmas I spend 40 hours a week at least turning, as soon as I get home from the office I'm out in the workshop, all I have have to give up to do this is the sitting in front of the TV with a bottle of wine, I still do the other stuff, But I love the creating and the sense of achievement seeing something unfold from a piece of wood.
Some people will do it as a way to earn some extra cash, but many will do it for the simple reason that they just love doing it.
Ed