It's an unpleasant and politically incorrect idea that despite clearly being the experience of most normal men you talk to about these things, is probably career-damaging to academics who would research it honestly so you see it backed up in that regard either by amateur blogs or very cautiously worded "respectable" research.
Think of harems in the old days and alpha males in some species in the animal kingdom.
Tinder and the like (so the theory goes) apply a massive magnifier affect to the natural tendency of "elite" men to clear up.
Side note: the tactics of average men mentioned elsewhere in these comments such as swiping on everything, and similar techniques are effects of this phenomenon, not the cause.