Because they are still seeing him as "Dev Dixit's brother' and not Baldev Tripati's son. Vickky was never treated as an individual. He working as a manager is not bad as himself, but as Dev's brother it is beneath their status according to them. And that is what is acting. RR needs to stop feeling entitled and start behaving herself of being a Tripati, separate of Dixit's identity.
Vicky should actually take that lesson from Sona. She didn't use Dev's name and built herself up.