My guess (from experience with using a Macbook at work in a similarly large IT company) is that their corporate Windows image has a huge pile of shit bundled into it for historical reasons that breaks all the time, while the Mac image is relatively frugal.

I can observe a slow tendency that our corporate Mac image piles on more and more junk over time, probably because more people are using Macs than the year before and thus IT allocates more headcount to work on Mac customizations.