Even if you use NS as DC-AD/File server at home, you will want to protect your children by their “youth mistakes” and you will want to see what they do. 
But, I always talk about NS as a professional product.
In a company network, there are no “private data”.
If you may have access to personal email, cloud, …, all those have nothing in common with company data.
All data in the network are property of the company.
The access to those data is hierarchically.
As system administrator, as the most trust person in the company, you need to have access to all, for different tasks.
In a small company, where the owner is also sys admin, he must have full access to all data.
In Windows, when you create a new folder, there are from start some “users” that have full permission to this folder (SYSTEM, Administrators) and others with limited permissions (Authenticated Users, Users).
Always, you can restrict or expand those permissions and/or add new “users” with proper permissions to this folder.