It’s a liability and risk concern. If something were to happen (and this is guaranteed to happen eventually) you want to operate with the lowest privileges that you can to reduce the potential damage. This can be a mental health issue, a disgruntled employee or a simple accident that leads to compromise of company data and systems. For the same reason you don’t want to run every single application as administrator, you don’t want every employee to be an administrator at all times.

That said, with a good company, it’s not that difficult to get the access that you need provided that you have a legitimate use case. As a developer, I have a script I can run to give myself full administrative privileges at any time. Think of it as a safety on a firearm to ensure it’s being used deliberately. Even then, I don’t have access to the same documents that HR does because I don’t have a reason to know everyone’s data. In personally, I don’t want to have access to everything. If there were to be an incident (again, with infinite time it will happen eventually to somebody), I could become involved simply because I had access or knowledge. As I gain more experience I learned it’s often better not to have access to information.