Even in cases where you have a Credit Card, there are many hoops to fly through before you can make an in-app purchase:
- It must be an international credit card
- It must never have 3d-secure enabled
International Credit Cards are costlier, and it just takes one payment on an Indian gateway to enable 3dsecure accidentally. And then, you can't use your card again on any international purchase because no international gateway supports 3dsecure.
Are you trying to say that Indian credit cards that are 3D-secure enabled don't work for IAP? This is absolutely untrue. I have both AMEX and Visa cards issued in India, and simultaneously use them for domestic and international online purchases, IAPs, and in-store. Never had a problem. Frankly, I've never heard this.
So, if you make a purchase on an Indian website, you get 3dsecure, but you don't get one on an International purchase? It used to work fine for me till a while back, but the newer RBI guidelines have specifically mentioned 2 factor auth against international transactions[0]. Since its just a guideline, it is not enforced as such equally by all banks.
An app can authorize a purchase through the phone provider. A website requires a credit card.