Because, back in the day, 98% of games were being developed for, the IBM-PC compatible machines, and I guess back then having an IBM-PC Compatible computer was the standard. It's like why aren't games made for Linux? It's been around since the early 90's, and it is a lot of work to just install anything in Linux. But Linux isn't the standard, Windows is. So 98% of game devs are going to only develop for Windows operating systems.

The other 2% are people who will develop for other computers and/or operating systems. I remember when I was maybe 13 or so, and I was reading a computer magazine in 1989, and I remember turning to a page that had 100 computer games, and it showed a list of IBM computers and Mac's. Every game was checked off for IBM, and like 6 games were checked off for the Mac, and all 6 of those games were the most obscure names of games I'd never even heard of.

But that's basically the gist of it all. IBM-PC compatible computers were the standard back then, and I would like to say that they still are, with Windows being the standard for operating systems. I highly dislike it because my choices are limited with what I want to do, what company's hardware and software do I want to use? Oh, looks like it's either microsoft or apple. Not much choice unfortunately. And for me, Apple died with Steve Jobs.