Vincent and his people do what they believe is right to keep control of their people.
From Inside the Grey House:
Natalia took a deep breath, not liking his tone of voice. He was talking to her as if she were a disobedient child. Her eyes narrowed as she realized this was the second time today someone was trying to make her feel like a child. She let go of the annoyance as he raised an eyebrow, waiting for an answer. “Order must be maintained.”
“That is correct.” He reached out and pinched the tender wound on her left breast. She cried out in pain. Joseph pulled his hand way and gave her a hard, mean look. “You came to us looking to be saved from Zachariah. We understand you can be an asset to our house and family. Don’t make the mistake of thinking that you’re not disposable. Vincent may enjoy having you in his bed, but if you take too many risks that endanger this house, I will take great pleasure in torturing you in many different ways before draining all the blood from your veins. Any time you consider going against Vincent’s word, remember this wound; touch the scar. Let it be your guide. Now get up. We’re done here.”