I'd say MOST companies, not fancy in the public eye/media ones, simply use a computer as a tool to do a job.
In exactly the same way a mechanic has tools to fix your car.
If you fix cars, or do business, you want a very flexible tool, you can use in many ways, that is compatible with the majority of things that you in your business may every come across.
You are not interested in the computer, what it looks like, what colour it is, how thin it it. It's a device, on/under your desk that you don't care about as you are focusing on your company business.
So you get a PC.
Apple is making no reasons to change that.
As a tool, iMacs and Mac minis are perfect. Much less viruses and malware than Windows, more reliable and software is plenty too, so choosing Mac has less maintenance costs in long run. So businesses do choose Macs, especially now with abundance of iOS devices around.
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I believe that main expansion is still experienced consumers, gamers, DIY guys. These are mainly budget oriented people who don't mind tinkering with their machines. For them, iMacs and Mac minis are too limited; so having a midtower xMac with some customization will be good choice. I don't think it will eat much into low end iMacs, because they are pretty much well priced.