It is very common because it is not benefial for the company to clarify reasons. It includes many risks.
They can be proved to be incorrect, for exmpale if they refer into their own ToS, which is public information and binding. And then some legal expert says that this is not how it goes and it ends up into court, because customer sees risks being lower.
If they made a mistake or there was a software failure, it is bad PR.
If they ban someone for some specific reason but not someone else, there will be drama.
They can be proved to be incorrect, for exmpale if they refer into their own ToS, which is public information and binding. And then some legal expert says that this is not how it goes and it ends up into court, because customer sees risks being lower.
If they made a mistake or there was a software failure, it is bad PR.
If they ban someone for some specific reason but not someone else, there will be drama.
It is very beneficial to just say nothing.