>>10917247It's a result of the art style. A foxgirl will just end up looking like a catgirl because the ears are pointy. To make a doggirl, you need to use an ear type that is notably distinct from cats, while not being overly confusing. This just results in floppy eared dogs being used as a basis, and it just looks awkward.
Also because usamimi weren't an option. Cats are the superior pet.