I think it's that the same dynamics that go on between any close relationship go on here. It's just particularly intense between mothers and daughters.
Part of the reason (motherly advice) bugs us as daughters is because our mothers are so powerful in our lives. They loom like giants. The reason mothers keep at it is because they're so powerless. They cannot get you to do what is so obvious to them you should do.
It can be the best of relationships and the worst of relationships - often at the same time. The bond between a mother and daughter is one of the strongest, but it's also among the most complicated.
Like most men, my father is interested in action. And this is why he disappoints my mother when she tells him she doesn't feel well and he offers to take her to the doctor. He is focused on what he can do, whereas she wants sympathy.