I find this a lot too, but I think better roleplayers CAN make this work. One must keep it to a minimum, though, to prevent "The Revan Disease"; a Sith who has a quirk or a soft spot is three dimensional, a Sith who seems like a Jedi who wandered over to Korriban is bad writing (especially for roleplaying) and makes "rare" characters feel all too common.
Somewhat similar is the red Twi'lek thing; in universe, red Twi'leks are supposed to be about as common as albino humans. Yet, some of the most common Twi'lek colors aren't even available, and Lethans (red Twi'leks) make up about 2/3 of redside Twi'leks. See here