It occurs with some frequency as a means to show nobility without the usual vices associated with royals, this is compared to figures such as Conan or your thief/smuggler that are world weary and wise while denying any form of title to themselves and being part of the common-folk/working class background. Disgraced/poor noble then is the means by which nobility is made palatable to common people when in reality most nobles and their actions you read about in history books are legit just sociopaths or incompetent failsons/daughters.