That's like a lessee changing the locks and locking a landlord out of their apartment.
I can assure you, this is quite normal and perfectly legal
behaviour in the UK and indeed, much of Europe. Whilst you are renting, you have exclusive access, and the landlord would be committing an act of trespass if they entered your apartment without your permission and 24hrs notice. (Except in an emergency obviously).
In some parts of Scotland, the landlord might also get a smack in the mouth into the bargain
Similarly, I can think of plenty of examples where only exclusive access to a hosted server would be acceptable (perhaps even legal), due to strict security or data protection requirements.