Cause there have been more Lesser and Mojave around than Fire when both were proved out to create BEL. So more people were able to produce these.

Also Fire are a nice morph, but compared to a lesser, people will want lessers. Fire looks like high gold yellow as babies, and when they grow they get better. Lessers looks like something totally different than a normal, and when they grow they also look better IMO.

But Black Eyed Lucys are a needed morph, just for the fact that you can breed anything to eat and it will be Fires. Breed that BEL to a Super Pastel and you have 100% FireFlies, who wouldn't want something like that ?