Bank account/parents

When couples get married should parents be allowed to be on their bank account? The reason I ask is because my brother in laws parents are on his bank account. And also on all the other children’s accounts even the other two siblings that are married. I am the only sister in law in the family where my in-law are not on our account. So to move forward the brother in law is dating this girl she has asked him that when they get married if he will take them off as in not have the parents on his bank account. He doesn’t want to take his parents off his bank account. So what should she do? She’s frustrated because she doesn’t think it’s appropriate. Is she wrong?