They may feel something they are getting in return makes it worthwhile. They may truly feel like their place in life is to be treated like that. It could be they are in a situation where they cannot easily escape from. What to do?
You can always stand up for yourself. You need not tolerate someone treating you like his or her servant. You are worth more than to that. Please, never forget this. People may try to convince you are worth less than they are or you have less human dignity than they. Do not let them.