Even when I was very young, I wanted to be a writer. I blithely assumed I would be able to make a living at it. It took some years for the reality to set in: being a full-time writer was possible, but the odds were against it. So I started looking for something else I could love as a supplementary career. I went through a few permutations, but found that I kept coming back to other creative fields - none of which were particularly lucrative, mind.
Somewhere along the way, I realized that I didn't want to be a full-time writer. For me, the coordination of having a second profession had become an important part of my life and even an important part of my writing. There are two reasons for this, I think. The first is that I am an incubator: I do much of my thinking and plotting on the backburner, often while doing something else. If left with "only" writing, where would I go to allow my projects to simmer?
The second reason is that life itself is fodder both for story ideas and for the finer details of writing, from character quirks to snippets of description to unexpected reactions. I wonder if missing those other aspects of life would turn my writing too far inward, too dependent on itself ... and that would be a shame.
Now, all this said, I wouldn't at all mind making enough that I *could* stop other work, and any other income would be gravy ... but that's pie in the sky.