If most guys have to have confidence to get a girl why do women expect men to be committed once they learn this skill?

I don't know if girls can grasp this concept but if a guy isn't confident then he gets no girls. But if he takes the time out to learn that skill so that he can attract women, why do girls feel like he should stay with one if he's now learn the ability to attract multiple?
If most guys have to have confidence to get a girl why do women expect men to be committed once they learn this skill?
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