It's kinda terrifying how often that happens. Something I've learned being around vulture culture is to be very fucking careful buying bones between the fakes(things like coyote teeth/claws being listed as other predators) to the highly illegal bone trades, be it human or protected/restricted animal(or even illegally harvested, which is pretty common).

Human bones are sold quite frequently for educational reasons. Wife used to have a skull for her medical studies, but gifted it away to her niece

Just a quick DDG search and found a lot of online shops selling them

Why not?