Attractive people will have options, so the app has to show them other attractive people to retain them. That's why there is a containment system where if your Elo drops low enough you get shown other low-Elo accounts. You also need attractive people to retain the low-Elo accounts (Elo being a relative measure to the userbase, by definition) so you can seed them with attractive people once in a while but generally keep them confronted to low-Elos. Ideally, you want to create an impression of potential at first, which will get the user to spend in the face of loss aversion as the Elo bucketing sets in.

That said, this is not the only thing happening, and the platform apparently also does the opposite, or does batches (exclusively low-Elo followed by exclusively high-Elo for a while). At the end of the day, it's an ML blackbox.