You know... I think the Nighten gale equipment is exclusive to Thieves of high ranking. On top of that, Nocturnal prefers the company of skilled and disciplined thieves. Not street rat thieves.
On top of that, deals with her usually comes with a form of rebuttal that just make things not worth the trouble.
Like what happened with the gray fox. The gray fox stole the cowl from Nocturnal. Though she didn't seem to give two fucks about it, and just allowed it to happen. The cowl cursed the man to anonymity until he wears the mask.
The nightingales aren't granted a peaceful afterlife. Nor are they to be known.