Interesting - thusfar, I'm the only person who does b&w on camera.
Why?
I still try to do little post-processing, and try to do as little as I can. A crop, a resize, maybe a little lightening, but that's about it. Not because I think post-processing is cheating, but because I'm just not good at it yet
And for me, still fairly new to the world of photography, it's a different learning experience to shoot in B&W instead of color.