Gender locked race?

[Gwenorai]

The females do because that's how their feet are structured, similar to a bunny standing on its hind legs. Because, you know, Viera are bunnies. Going by That Concept Art™, the males have the same foot structure, so it stands to reason that any footwear they'll come with should offer similar support.
Namely, high heels.

Concept art shows that the males don't actually have the heel. So it might be less about support and more regards to their culture.