Compared to what we could be as a society, people have pretty low self worth. Most people are constantly gossiping, fighting, putting each other down, socially anxious, etc. Guys talk shit about each other just to impress girls they are desperate to get. Girls talk shit about each other and guys and then desire to date those guys. Even those who seem narcissistic actually typically have low self worth. Someone who truly thought they were better than others would have no reason to brag to the people who they supposedly feel superior to. Just as someone who thought they were better than everyone would have no reason to brag to others, someone who had healthy self worth would have nothing to gain out of all this gossiping, fighting, etc.
Women want a man who is alpha, someone higher on the social hierarchy. Part of this is evolutionary, part of this is their own low self worth. The lower a female feels on the social hierarchy, the more she wants an alpha boyfriend to help balance this.
When a woman is with a man for awhile, it negatively skews her idea of him. "I'm lower on the hierarchy than him, and yet he stays with me, he must not be great after all." Those words don't actually go through her mind, I'm just putting into english the subliminal thought process.
This is why women never stop giving shit tests. They start to think less of you (just for being with them) and need to confirm of refute this idea with shit tests. You don't wake up everyday and say "hmm, i wonder if the sky is still blue, I better go check." This is because if there is an obvious truth, you don't bother to check it. Yet, women still wake up everyday and say "I better make sure he's still alpha" (subliminally).
So, what happens when the next chad comes along? She now thinks less of you and thus she thinks more highly of chad. We all know what happens when someone comes along who she thinks more highly of. She either leaves or cheats. Hence the current status of relationships in our society.
Edit: I forgot to mention, this is why women hate beta behavior so much. If she thinks low of herself, how low is she going to think of someone who worships her? On that note, this is why women love "the jerk." She thinks he is above her, treating her in the way she subliminally thinks she deserves.