Some people like messing with cars. They take the time to understand what's happening and learn the process and pitfalls. Hobbyists wiil never be as good as trained professionally but we can still get the job done. I went through the trouble to diagnose and replace a bad alternator on my civic after the battery started dying too fast. I did it cause it was fun.

The other reason i did it is because the dealership and other shops quoted me over 10 times the cost of parts, and I literally did not have the money to take them up should i have wanted to. Car maintenance is expensive, _especially_ at the dealership.