Well, I imagine it's a bit frustrating when you google for something, find an interesting project or product, and then it's only available for Windows. But I believe that anyone who decides to go with a minority platform is aware of this before they dive in. (I used Linux for a number of years when a job allowed it, but I knew I'd have to make some sacrifices).
*nostalgia enters* And back in 1991-2, when it became obvious that the Atari ST line of computers would come to an end and not play a major role in the following years, I would have loved to switch to a Mac, but not only was it substantially more expensive than a DOS/Win machine, even then there was less software and fewer video games available for MacOS. Since I was working in the IT/entertainment field (had just started), I wanted a large, popular platform. So I went that way rather than with picking up a Mac, which -- had everything else been equal -- would have been my preferred choice.
I still believe Macs are nicer systems and offer a better experience than the typical Windows-based boxes, but the situation is no different than it was two decades ago: if you want to have the widest selection of software (especially gaming related stuff), the cheapest hardware and the largest audience, you need a Windows machine. For small developers of what is essentially a nich� product, like Ash and Tom, prioritizing Windows is an absolutely sane approach.