It's open source, if you want it, you can add support for it. Which is a lot more than what you can do for a lot of other development tools that only run on Windows and have lackluster or no support on Linux.

Also, they might just not have Windows developers or a use case for running the tool on Windows, so even if the cost of adding Windows support was zero, they'd have to go out of their way to test it. A lot of open source code might run just fine on Cygwin, but most people choose not to support Cygwin because damn near no-one uses it anyway.