Xamarin compiles through XCode, so having Mac somewhere is a requirement. Any platform that compiles for iOS would have this same issue. I think the MS is pushing Xamarin Forms because it could eventually become a more direct competitor to React Native. In theory, you could remove the compile requirement for a Xamarin Forms only project. I am a C# guy, but React Native is attractive and Xamarin needs to have a compelling alternative.
Other platforms like Codename One ( https://www.codenameone.com/blog/comparing-xamarin-and-coden... ) can provide things like Java support for iOS, Android, Windows etc. without a physical Mac. They do it thru a cloud build process. It works properly because of the lightweight architecture.
Obviously the goals of Codename One and Xamarin are different whereas Codename One tries to be WORA, Xamarin doesn't.
The downside is that offline builds cost $399/month, though I would hope that they would make this functionality available to everyone if for some reason the company shut down.
