Women have the upper hand in dating (as men are more horny and women pickier), and therefore women have power on establishing relatinships too. However, high value men are scarce, so they use sex to manipulate them into relationships.

Average men do not have a chance to manipulate women into sex promising relationships because no one wants relationships with them in the first place.

High value men get sex anyway, with that woman or another, so often women feel cheated because those men do not offer a relationship even after getting sex from her... while the fact is that she tried first to manipulate him using sex!