Earlier quoted context omitted.
That's a very good point - but for what we do (on-premise version control for Excel where each workbook version represents one object) we won't be getting even close to that number. But yes, agreed, it entirely depends on your use case.
If you don't mind me asking, why not use Amazon S3? It's cheap and -- importantly -- somebody else is on-call for its uptime.
I'm going to guess that it is part of the "on premises superstition" where companies feel that the stuff they own is more secure somehow. Obviously, this is not often true in practice, but 5 years of research/consulting has taught me that they feel this way all the same.
Occasionally, there are laws that also mandate certain controls that cloud providers in general did not have. That is also becoming rarer as time goes on.