It's important because we can bitch about origin characters all day long (and I'm right there with the bitching side, my first major post in this forum was me bitching about origin characters) but we are a minority in this as far as I can tell.
Maybe we are, maybe we are not, and if we are, how small of a minority : 5% ? 25%? 45% ? I don't know, and I feel it doesn't matter much. I think catering to the people who won't play an Origins companions, but instead a fully custom PC, costs a fraction of what it takes to create merely one Origins companion. (Creating an Origins PC/semi-custom PC would probably take less, as I assume a lot of voice acting won't be needed.) To a very good extent, the fully custom PC is already there. If Larian can give us a couple of options at character creation, all the better, the most important is to not remove options.