User cases for Non-production robot / testing robot

I do not understand the practical use of non-production robot and testing robot, can somebody tell me how and when to use them?

This becomes even more puzzling when it is clear that production, testing and development orchestrator generally do not even share the same server and all are set up on their own.

Then what is the point of non-production robot? Testing Robot?

Adding to this, what is the point of defining a studio robot?