The descendants of the family have to set themselves apart one way or another in order to be appreciated by the family. Shawn made himself stand out by becoming a lamp bearer.
His decision to become a lamp bearer restricted his actions and made him unable to enjoy some of the things he used to be able to enjoy such as raping women and beating servants or death or taking anything he fancied from a commoner including their wives and children.
As a lamp bearer, he had to live as a law-abiding person, or the brand on his chest would punish him severely. In exchange, the family rewarded him for his sacrifice with a big house and a lot of money. With money, he doesn't have to rape someone to have sex with them. He can coerce them with money, so he hasn't lost out too much.
