There are lots of people who would be interested in getting their own skull! Institutions (Universities, museums etc.), students learning human osteology, anatomy or dentistry, and artists are usually who would be interested in buying human skulls. These respectful homes often use them to study, teach, or learn!
So why can’t students use skulls at school?
While usually schools and laboratories have skulls to study, students may want to study in time where they don't have access to the specimens. In this case, they may want to buy either a skull or a replica skull to assist them. Alternatively, museums or institutions may want to add to their collections to help researchers or students in their facilities. Not every institution has a modern body donation program or the facilities to process remains.