Apple is not alone there. A lot of people don't realize, but Windows is (or at least for the longest time, was) in the same boat. You need to have a Windows machine to build Windows app.

I believe, but I might be wrong, a similar thing applies to a large number of Linux systems especially if you wish to build GUI apps.

P.S. Windows even used to require a paid version of their IDE Visual Studio for the longest time and a hefty subscription fee for MSDN. And, don't forget the concept of "Developer License" for things like SQL server.