Writing has to be one of the most hazardous occupations in the world. First of all, it requires you to sit down, virtually immobilizing yourself, at a desk or workstation that may not be designed for optimal human endeavor. It requires very little exertion to be a writer. You can work hard all day and burn about 12 calories and still feel tired when you get home.
Second, it creates an insatiable urge to eat sweets. Maybe all Americans have this, but writers have motive and opportunity to eat more than their fair share of donuts, chips, soft drinks, and other things.
Third, a lot of writers don't earn as much as they would like, so they eat at the lower end of the gastronomic spectrum, tending to go to places where you obtain your food without having to exit your car (thus not burning precious calories).
Fourth, writing can be a fairly stressful job if you consider not having a steady paycheck and exposing yourself to every flamer in the world who wants to call you an idiot.
So why do we do it? I don't know. I suspect that if we had other skills or inclinations, we would have gone on to have successful careers. But I have always found a lot of satisfaction in the work. It's fun. It's challenging. It doesn't get boring or old. It's an adventure. I've met lots of great people through writing I otherwise never would have got to know.
I guess I became a writer because I didn't want to work for a living.