The main thing keeping people on Windows is not actually IT departments per se, but large software companies that have longstanding monopolies on certain indispensible programs used in professional environments, and who arbitrarily refuse to port said programs to Linux, for who knows what actual reasons - maybe Microsoft is "making sure" that they never do.
Such as:
-AutoCAD
-SolidWorks
-Adobe suite
-ArcGIS
-Alteryx
These programs also typically are so complex and/or bloated that they break Wine.
Etc.
Or in blue collar work, the programs they use typically also only run on Windows - or maybe they'd run fine on Linux with Wine, but they don't have time for that.
Ask a white collar guy why he can't use Linux and the answer is going to be something like "well, _______ program that we're paying $5000/year for only supports Windows"
World's foremost 486 enjoyer.