The problem is that even with a no-hassle refund process some customers will still call their credit card company and ask for a chargeback because it's a process they're familiar with and it's easier for them to do than to go through any kind of custom process you've built for them. I imagine after dealing with customer support BS enough times your goodwill is eroded and you're just going to choose the path of least resistance for yourself.

Not everyone who does a chargeback is looking to get their money back.

Some do it specifically because it will harm the merchant. Especially if they feel they've been wronged.

> I would imagine all purchases to be a low dispute risk, as the merchant can simply offer refunds to all no questions asked.

That only works if you offer a no questions asked refund, and even at that, that doesn't imply 0 risk. Cards get stolen and tested on low value purchases all the time; if a scammer decides to check 1000 credit cards on your app, you're going to have a very bad time.