When a software license has been acquired and installed on a server (either physical or virtual), it is assigned to that server. It is very common for software vendors to disallow licenses to move freely over servers.

One of the reasons for software vendors to disallow free movement of licenses is to prevent customers purchasing a single license that can be used for 24 hours. For example, in a scenario where a customer is using the follow the sun principle, software could follow shifts of people working in Asia, then to Europe, and then to the USA. Another reason is software vendors' fear of reduced income when a virtual server running in a multitenant infrastructure is shared by multiple organizations. Instead of selling a license to each organization, only one license would technically be enough.

It is a bit like if a car manufacturer does not allow his cars to be used by a lease company. The car manufacturer only allows selling to consumers directly.

It all comes down to...