Well, I would point out that my experience writing comics was not typical. I was writing them as an extra part of my job here at LEGO Group, but I wasn't being paid to do them and I didn't have to compete with someone else to get the job.
I have not made any real effort to write comics for the big companies, but I gather it is very difficult to break in. They tend to have a lot of "hot new artists" coming and going on comics, but the same writers year in and year out, often doing four or five or six books a month. Recruiting new writers just doesn't seem to be a priority in the industry, which is part of the reason why (as one industry vet put it), stories now are more about who can beat who and less about characterization or actual plot.