As sometime who has worked full time on this for over 5 years now, I have found a few aspects of your answer:
The technical challenges of doing it with credit cards are overwhelming (in CC parlance, a "microtransaction" is anything under $10) due to fee structure.
You can simplify this by using a different payment rail (in my case, Lightning over Bitcoin), but now you have a different problem: nobody has Bitcoin.
You also need to add the lack of convincing incentive: since microtransactions don't yet exist, there's no proof that that's a market for them. That leap of faith is a significant barrier.
The technical challenges of doing it with credit cards are overwhelming (in CC parlance, a "microtransaction" is anything under $10) due to fee structure.
You can simplify this by using a different payment rail (in my case, Lightning over Bitcoin), but now you have a different problem: nobody has Bitcoin.
You also need to add the lack of convincing incentive: since microtransactions don't yet exist, there's no proof that that's a market for them. That leap of faith is a significant barrier.