::looks at the plethora of burns, blisters, and cuts on his hands and forearms:: ya lets no go into the injuries. Like blue_wolf it was a paycheck, I started slinging pots and pans at a family restaurant when I was 16, when a position opened on the line they asked me if i wanted the job, hey it came with a pay raise I was all over it. I ended up staying there for 2 years and while it was just a family restaurant I got an oppurtunity to work with some talented chefs, even at this point it was still just a job. I moved on and was working for a newspaper doing computer programming and while the pay was decent it was, well, dulldrum. I often caught myself thinking of when I worked in the kitchen and the fun I had had and the things I had learned as fate would have it, I wound up working back in kitchens and never again left them.
To answer your question "Why do we do it?" I do it because I enjoy it and the people I work with, all the way from the Executive Chef to the whinny server who describes pheasant as "Its kinda like chicken" to the brain-dead bus boy who has obviously smoked more then his fair share of weed. Its going home at the end of the day and hearing "You guys did an outstanding job" from the GM, watching people sit and enjoy their meal, or simply getting to be creative with the food you produce.
Simply put, I do it because I love doing it.