But, they haven't "done good" by vendors, by and large. A YouTuber with viewerships as high as mainstream TV shows can barely afford "2 guys and a mic." App store purchases is a fairly meager market, and not a place to build a serious business unless you have other "monetisation" plans.
Steam is somewhat of an exception but still, being beholden to a discovery algorithm like that is disheartening.
Recommendation engines are such an important part of any market these days. Besides recomending stuff, it's an incentive structure for the market.. a la google-> seo spammers, fb-> kgb spammers, etc.