You are partly right. We have been told that we would never be enough no matter what. Since we were little girls. Then, at some point we notice that many men only care about our looks and how pleasant we behave towards them. At that point, we do noticed that they aren't working that hard to be pleasant to us.

And, lets face it, many women are feed up and think that if those men think that we aren't good enough, maybe we are better without them. So we move on to men who like us the way we are. Those men aren't perfect by your standards, but they are by ours.