It's about deployment. Anytime you use Windows in a cloud hosted environment, you end up spending more on licensing and needing larger instances -- increasing the costs and startup time. I can easily development on Windows and auto deploy on Linux instances when I'm using either Python, C#, or NodeJS. But if I am going to be using Unix like environments anyway for deployment, why not use a Unix environment for development? MacOS gives you the best of both worlds -- a Unix environment for development and polish for everything else.