Valid reason here, at least. They directly oppose the GNU General Public License and all freeware released under it, which I work tirelessly to support and improve. Mostly because, at least in my opinion, you shouldn't have to pay for your OS, your web browser or certain tools (mostly the "Office" type software).
I'm perfectly willing to support companies like Adobe (who release certain of their software for free (Adobe PDF Reader and Adobe Flash Player, notably) and you're really paying for quality with their other products), but Apple tried to get the Free Sotware Federation shut down on the premise that "they're costing us millions in revenue." Any company that complains about "losing revenue" to freeware when they're making trillions every year deserves neither your money nor your loyalty.
I've said this before, but the second Steam announces support for Ubuntu-style Linux, Windows XP is gone from my computer.