I don't think it has anything to do with security, it's software compatibility. The majority of the software that's written for the enterprise isn't written to run on Macs. Plus corporate America is just now starting to take security seriously, but that's because of external pressures like PCI, FISMA, and HITRUST (plus the rise of ransomware).
I'm 20 years in IT, what disaster was there in corporate America from going to XP? XP on the Desktop ran really well, especially once SP2 came out and Server 2003 was pretty solid. We migrated our environment from NT/Novell to 2003 AD domain and had very little problems.
The only OS I'd call a disaster was Windows Vista.
Apple has never been B2B. All of their products and services are geared to consumers vs Microsoft which heavily targets corporate clients (Windows Server, Exchange, SQL, O365, Sharepoint, etc).