The key is that he's not even an affiliate. His cut is coming from his customer, not from Stripe (he charges 1% on top of what Stripe charges the user). There

The key is that he's not even an affiliate. His cut is coming from his customer, not from Stripe (he charges 1% on top of what Stripe charges the user). Therefore Stripe doesn't have a financial reason to build this app, they already collect the same fees from these users.