Carbon can command a higher price, and (I presume but am not sure) a little higher profit margin.

Oh, you mean for the cyclist. Compared to steel, weight is the biggie. CF also offers designers a little more control over tube shapes and maybe tube characteristics. So far, all the steel I've seen sticks to round or slightly oval tubing.

Nowadays, you can get almost all of the same advantages out of high-end aluminum, albeit with a 1-2 pound frame weight premium. IIRC several steel alloys can get close to aluminum for weight, but I don't know if you can hydroform steel to the same extent of as aluminum.