Actually, I was about to post what Mdogs posted and was able to just like his post. I wouldn't have worded it exactly the same, but he captured my feelings about it.
Few bass players use flats. Few basses come with flats. I've put flats on two of my six basses because I was looking for a particular sound. One is a five string fretless. The flats are tapewound as well. Part of the reason is that I don't want to cut up my neck. The other is a four string acoustic-electric. They help it to sound very much like an upright.
The other four use standard round wounds. And as someone pointed out, they will sound more and more like flats as time marches on. For must purposes, rounds are best. And for any kind of bright sound, they are pretty much required. But flats bring their strengths to the table too.
But to the main point, outside of TB, there is not much talk about flats.