Alternative to advertising for user acquisition

Recently the cost of advertising on effective platforms like Facebook that has good targeting tools is getting really high. User acquisition for mobile apps can even go as high as 30 to 40 bucks in my experience. Now why wouldn't app stores like google play or apple AppStore offer developers to pay targeted users to download their app. So the developer can actually directly pay targeted customer base to try his or her app. With cost of advertising going so high this method can make more sense. It would be great to provide an API that allows developer to set conditions before user can uninstall, in case they were paid for it.