2. ZFS, jails, stability (although the root reason at the time was "because people smarter than I recommended it"). In hindsight I can see how running some services works better on this system.
If you instantly switched over the average person and took away their Windows/Mac, they would be lost and would constantly get bit by the cons of those technologies. Ever had to teach someone something simple in Excel? Imagine how teaching them SSH would go.
However, that doesn't mean it can't be a gradual process that takes years or generations even.