What situation RDBMS need to vm or docker virtualization? Usually  RDBMS just have only one primary server for writing, so what's the point of virtualization?
It cannot make multi-DB, and one additional layer of encapsulation does not mean that the speed will be slowed.
But I know there's a reason for exist, what are the scenarios that are particularly suitable for database virtualization?
Personally, I really like the idea of putting a golden set of data in a VM or container for QA testing. Spin up a new VM/container for each project and you can test it in isolation. When testing is complete, it goes away cleanly. You can do the same thing for development: Think git branches.
I can't tell you how many times I've had projects look like they were failing because someone mucked up the data in the dev/qa environment to test a different project.