I don't understand how this can be enforced for selling digital goods online. Right now you can process a credit card transaction with only needing the number,

I don't understand how this can be enforced for selling digital goods online. Right now you can process a credit card transaction with only needing the number, exp date and CVC. You do not need the card holder's billing address. You don't even need the card holder's name. So what's stopping someone from buying your digital item (let's say an ebook or course where you use Stripe / PayPal to handle the transaction) but put in a fake address, or an address they don't live in. I don't think Stripe / PayPal will halt the transaction. Instead they might flag it as questionable but the transaction will still go through. In this case the business owner has no idea where the customer actually lives to tax them properly and the customer has no incentive to put a real address in because they are not getting something delivered to an address.