[TheRealSteel]

But why do they care? You're paying the transaction fees. They're getting their money. If anything isn't it good for the payment processor to get more transactions?

It's a real transaction. Nobody was deceived, the money really changed hands, and the payment processor got their fee.

If I own a physical shop I'm allowed to buy stuff from it if I want, why isn't that also the case for an online store?

I'm not saying it isn't against the ToS, but I agree with OP it isn't obvious why it should be and it seems like almost everybody would test at least one real transaction at some point.

[toasterlovin]

I think the issue is that one possible scam is to sign up for a stripe account, run a bunch of charges from cards you control, then when the funds from Stripe hit your bank account, you run a bunch of chargebacks. So this policy that allows them to ban accounts that have even a whiff of this going on.

[mohsen1]

It's self dealing in the context of taxes.