That's easy to answer. There are a ton of specialized software packages that simply do not run on Apple machines. It's impossible to justify the cost of developing specialized software to operate on Apple computers when Apple's market share is less than ten per cent.
Apple is certainly idiot-proof but a lot of people expect more than that and look at their computers as an important tool to get a complex job done.
Name one task that cannot be done on a Mac. One. Hit me with your "complex job."
My Mac can do any job I need it to do. Moreover, the newer Macs can run Windows, which means that they run the same programs that PCs. Of course, there aren’t any PCs that run the Mac OS so I guess the advantage here would go to Apple.