The lack of gender representation in some races (thankfully remedied!) was down to a cultural thing. The Padjal are pretty clearly a hyuran genetic mutation, understandably rare.

Funny though. The Galka race in FFXI (on which Roegadyn were based) appeared male-only, but were in fact asexual. They didn't reproduce but always had the same numbers thanks to reincarnation. Interestingly, you'd have young Galka that still retained knowledge of previous lives, leading to Padjal-ish situations where an apparent kid knows more than your grandma.