The sad things is that the people who do this then drag their own kids into the position they were in. Everyone ends up being there out of a sense of duty to everyone else. It's why I think the idea of being "PIMO" (Physically In, Mentally Out) is seriously flawed, misguided and unhealthy for all concerned.
Leaving, being the ones to make the break and take that hit, is a gift to your children and possibly to your parents too ... because maybe they are only going because you are.