The main reason for me is that Apple hardware is (from my experience) unacceptably unreliable and their warranty service is infuriating.

Add to that a lack of expandability, customizability, (user) repairability and (hardware) compatibility.

Life is just a lot less miserable without having to deal with Apple hardware. PC components seem to be very reliable when you spend just middle-range prices and you can easily buy and swap out components when something does go wrong.

I generally go many months without having to reboot my Hackintosh, and I can't ever remember having a kernel panic after initial setup. Both of those things were not true with Apple hardware.