Why, because of the satisfaction it gives and the learning that takes place with each job and so that if i breakdown I have a better chance of being able to work out why is it so and then fix it it. Also doing as much as I can as often as I can then have a better idea of when to cal it quits and pay an expert to do things I cannot or choose not to.
Also as RAG said above when your in the bush and rip a tie rod off on a stump its nice to know that a couple of pieces of wire and a short length of branch is all you need to get you home!
Pity this doesn't work at sea but then thats why you have two motors
Chimo