Referral marketing for iOS (in-app purchases and subscriptions)

There's already billions of businesses for referral and affiliate marketing with Stripe: Rewardful, PromoteKit, Branch.io, Viral Loops, +∞ more...

I don't see any specifically targeted towards iOS app developers. At a very high level you would need to integrate a few APIs: - App Store Connect API to generate referral codes on demand - App Store Server API to verify receipts

Is this a niche hole in the market? I'm assuming companies like Dropbox and Uber do it in-house, but is there no solution or demand for "In-App Purchase Referrals" specifically?

Thanks in advance