On the other hand, when something doesn't work on a Mac, people say, "Wow, this doesn't work on a Mac. The vendor should fix that!" If I can't open a certain file type on a Mac, nobody blames Apple. This is a much more sensible viewpoint. The software vendor is the one responsible for making their software work, not some nebulous "those Mac OS people."
When you're on Windows or Mac OS, vendors test their software there. They support their software. There are vendors that do that on Linux, too, and so their software works on Linux.
In actual fact, though, even in areas where official vendor support is lacking, Linux developers have done an unbelievable job at making things work. Instead of complaining about the few areas where things are difficult, I think people should instead be amazed at how almost everything does work, thanks to the enormous efforts of thousands and thousands of open-source developers worldwide. The things that don't work are all being worked on, and barring areas where there are legal difficulties (like video cards) or where hardware vendors make life difficult (like wireless), everything is coming along quite nicely, and with some patience you'll see that almost every "it doesn't work" or "this is hard" gets fixed as time goes on.