The cultural norms part is definitely an issue here too - a lot of the people trapped in these caregiver roles either have other family members calling them selfish for wanting something different (I think we probably need to recognise that coercive control can be commited by groups of peoples as well as individuals) or have internalised that idea and think they are being selfish themselves. Seeing someone worrying about being selfish when they have given up everything else in their lives to care 24/7 for parents who are constantly abusive and require more physical care than one person can reasonably handle is heartbreaking.