The myth must be from the weak men's perspective; envy clouds their view.
Discussion
It's from all men, because all men are scoping out who-got-who and they all see Mr. Asshat has a girlfriend and Mr. Nice Guy doesn't.
That there's an army of women who aren't with anyone, because they don't want to settle for either of them, goes largely unnoticed.
As does the fact that most women eventually end up with someone normal.
Whether in romance, career, or other areas of life, we are incentivized to notice behavior that gets people closer to our passions or goals. The 'weak mens' complaints are self-loathing because they do not know how to become, or maybe even what is, a 'good/virtuous man'.
Ignore or pity the people who focus on their pains more than their joys. They are too busy licking their wounds to see anyone else's.