They have the least lore or significant presence amongst all the races, aside from maybe the Mirialan. The most that the Rattataki have is Asajj Ventress, who is a very minor character in the universe and not as well-liked as others like Thrawn for the Chiss or Darth Maul for the Zabrak.
Funnily enough, Assajj Ventress it not a Rattatatotitaktatatouille, and Darth Maul is not a Zabrak.
George Lucas loves him some Dathomirians. So both got retconned into Dathomirians.