Natalie Cassidy, Helen Flannagan, Tina Obrien
etc may find that they just are not good enough actors to get other parts.
Natalie has moved into reality TV and fitness DVDs and Helen wants to be a WAG and glamma model. The younger generation know that even if they are poor actors (as many are) they can try their luck in these other fields.
I think the older actors just see it as a job. They get up, go to work and probably have a nice life, decent house, financial security, etc. and are content to stick with that.