I was involved in mobile game development for several years, but I’m no longer active in that field. In my opinion, one of the reasons they do this is to maximize Ad revenue. In this case, it’s obvious that if you see this warning on your product page, the quick fix would be to spend money on Ads to gain a few more users as soon as possible. This also creates a competitive bidding situation across the market, as more developers buy ads, forcing others to do the same to keep up.