Even though she and her brother are from a powerful clan and has a high position within the clan that didn't mean they could do as they wish. Could their clan contest against sects? the answer is NO. No matter how powerful a clan becomes they couldn't contest against a sect, the only exception to this is the royal family. They have enough power to contest against 2 or 3 sects together but that'd never happen.
Vishnu didn't care about others' thoughts, he simply followed them because he is curious to see how much power this master of his has. Even though he knew that she is above the core formation realm he wanted to know how much power he could become in the future and old man Arthur also suggested that he should broaden his horizons as it'll be helpful.
