The companies who have helped service small networks in the past have been hamstrung by the lack of tools to help with the problem. The networks they service developed as simple systems, usually built by a self-taught network amateur-turned-pro. Maintenance was break-fix only, meaning when something broke, the company called and they came running to fix it… hopefully.
As time went on, the best of the support people developed procedures and programs to periodically come on-site to do a system review of logs and user information looking for hints of issues before they become big problems. In some cases, an elaborate checklist was used to record disk usage, processor usage, etc.
The problem, of course, was that the support people could only see what was happening on that particular day. If something happened later, they would never know about it … unless the customer called.