Because most of the morphs weren't collected in the wild.
This site has good histories of the origins of most morphs.
So take caramel for instance. ONE snake was in a pet shop in a tank with a bunch of other WC snakes. Rich Z buys it and breeds it in 1991. Can you imagine how many generations have passed since then? There was no registry back then to keep track of things.
Cinder. Some guy trades a gravid snake of Keys origin for a gecko in 1996. Rich breeds her, loses track of which males he used, eventually breeds her back to a son, and the first cinders are hatched. But it takes years to test them against other forms of hypo. Meanwhile, the hets are dispersed throughout a bunch of other lines.
(Shoot- I have to go work...)