> It boggles the mind that anyone who can write code would ever use a closed source operating system.
Some of us want our work to actually reach people who don't write code or sysadmin their own computer, i.e. most people in the world. I, for one, think my effort is wasted if it doesn't benefit those people. So while working exclusively on a free-software platform is tempting from an ideological purity point of view (edit: and I envy people like you that manage to make a living doing it), I don't think I'd ever actually do it.
Edit: I should be more concrete and less snarky. Working on developer tools is good and necessary, and you can do that effectively on a free-software platform like Linux. But I choose to focus on end-user-facing software, particularly in the field of accessibility. I could work on desktop Linux accessibility, for the vanishingly small number of blind people who use desktop Linux (and that number is shrinking; one of my blind programmer friends just switched to Windows). Or I could target one or more of the mainstream platforms where the users actually are. I suppose I could work exclusively on web applications, but I don't think that would be the best use of my skills. And even then, while I could develop primarily on Linux, I'd have to test on other platforms too.