Thanks for taking the time to write a thoughtful though flawed response. The thing is, I never mentioned Linux. Furthermore, I would say that the continued existence and popularity of the Apple Macintosh refutes the rest of your arguments hinging on ease of use and technical support. In fact you have perfectly illustrated the point that I am making here.
There was a time when doctors routinely prescribed smoking cigarettes as a quick and easy fix to all manner of ills. The long term hazards and effects weren't properly understood, and by the time they were, there was such a huge vested interest in perpetuating the smoking habit that the battle to remove it for the common good is still far from over, and may never be.
Likewise it is all too easy to facilitate yet another Windows installation, rather than risking your income by swimming against the tide. Even if you already know that the software that you are installing is inferior, you will go ahead and install it anyway, putting your own self interest ahead of those of your unfortunate clients.
As for the attitude of management towards this corruption that is so pervasive throughout the industry, I think a quote from one of my own past employers sums it up the best. "If we adopt this other more cost effective technology it will reduce my departmental budget and then Bob (the manager of another department) will get a better parking spot than me."