But failing to do so leads to increased operational costs, as customers contact CS again and again, demanding the rationale. It can also lead to negative press.

It's pretty easy to no longer support someone who is banned. The negative press is usually OK because like in this case, and in many others I've seen on HN, the one complaining is usually in clear violation of stated policy. It's completely reasonable to disagree with and complain about that policy, but they rarely do so explicitly, it drums up more support when the policy violation isn't made a highlight.

What specific violation of stated policy are you referring to?

I wasn’t being specific. When I said that policy, I mean the policy the company invoked to justify the ban, which the customer may not know.