Principles that Im referring to are e.g. abstraction and 'divide and conquer'. IT exists to make things simple that would otherwise be hard (to put it simply). Why would you deliberately abstain from using an abstraction that makes API testing easier and faster?

We've gone well past that now though and are back into making pointless and unnecessary complications to differentiate products so 'new solutions' can be sold managerial types.

Adding a service that needs to authenticate adds more steps and more complication. It's not making the task easier.