I use Server 2008 R2 (and upwards) at work and its really not bad, it's miles ahead of the previous versions which were horrible to use. Is it not possible that people use this stuff because its useful?
And my point was perhaps the reason people are using Windows server is not because Linux is too hard and unfamiliar but because just maybe it's a better fit.
If everything in the MS ecosystem "just works" then I am either willfully overlooking its great features or like so much else, it's a function of what you know best.
There's little to gain by switching to another OS if you have enough money for licenses and you know its ecosystem well.