Power Bi Rest Api App Endpoints

I am trying to interact with an App on a workspace using a service principal. The documentation states that service principals are not allowed. https://learn.microsoft.com/en-us/rest/api/power-bi/apps/get-reports

I have two questions:

1. Why is this the case?
2. What is the recommended path querying a power bi app from a back end process?
   1. Creating of a "service user" and getting a token via username password? This seems like a bad idea because we need to add, update or remove reports from the app to present to users. The "service user" will need admin rights.