Your own expectation is covered in the second paragraph of my previous post, I am describing
the expectation, which is what I and the other poster have described. You speak of this as an
assumption, but you have it backwards: given google's history of failing to meet our
expectations, we
assume they will continue to fail to do so.
Your question of "why" boils down to asking, What is to be gained by employing the principles of least privileged access, as well as proper authorization, auditing, and alerting? The answer to that question is beyond the scope of this post, but I trust that you understand or can understand the benefits of these principles.