Imagine that Alice runs a service where you can send people greeting cards.
Bob decides he's going to use this service to cause trouble and instead of normal greeting cards, he sends people messages with hate speech, such as their race, their religion, says he hoped they get cancer, and so on.
Alice sees Bob is doing this and it violates her TOS on the service, so she cancels his account.
Should Bob get a refund?
If he does, then Bob will have used Alice's system to do bad things in a way that actually costs him nothing. He's costing Alice administrative fees and regular costs.
That's why ToS violations should generally not trigger a refund.