Because het females are cheaper than visuals.
At least that is what I've always thought. And with some of the rarer and more expensive recessive morphs, het females might be the only ones available for a long time as the breeders keep the visual females for making combos later. And no, breeding recessive to recessive is NOT going to cause problems that weren't already there. At least, not unless you line breed for 6 or 8 continuous generations with no outcrossing.
Gale