There is a perception that young women are sexually or romantically attracted to "bad boys", while worthy, honest and kind guys are neglected. Redditors, or maybe millennials in general, seem to think that this is 1) unfair and 2) something new. It isn't either.

In the extreme, there are some men who consider themselves to be White Knights, and think they should be rewarded with the Fair Damsels' favor, just because of that. (In fact, floating around Reddit from four or five years ago, there was a hilarious essay parodying this which included a reference to, "watching your purse while you have a sexual encounter with a guy in the club's toilet". I haven't the time to track it down.)

There is, of course, an opposite gender role that doesn't get talked about as much on Reddit: the Good Girl. The one who is not having sexual encounters with strangers in the rest room, of course. Maybe they resent the women who are. I have no idea.

So the idea that being a nice guy is just a trickier, but according to the trope, mostly unsuccessful way of "getting the girl", is born.

It's all pretty silly and certainly nothing new. It just feels that way when you are young, because "nobody ever felt what I am feeling in the history of the world, ever!".