Lots of businesses build their own software. Do you think it's easier to deploy private software onto an iPad or a Windows machine?
[1] http://www.apple.com/ipad/business/it/management.html
[2] http://www.ibm.com/mobilefirst/us/en/mobilefirst-for-ios/
You need Macs to build iOS software. Meanwhile, you can find Visual Studio already being employed in most business IT shops to build custom desktop and web software. I can't remember the last time I saw a job ad for an iOS developer that wasn't for a one-off gig or a mobile apps shop (or a marketing agency).