Well, a Mac is needed to develop macOS and iOS software. But you can also use it to develop Android software; And in general, linux or unix software (either by

Well, a Mac is needed to develop macOS and iOS software. But you can also use it to develop Android software; And in general, linux or unix software (either by installing GNU tools and libraries, or via a virtual machine); And of course, also MS-Windows software in a virtual machine. And web applications and back-end (you can run all browsers, either natively or in a virtual machine). All this, with virtually zero system administration overhead, and nice non-programming tools for the occasional need. So to the professional software developper might prefer to use it. I use emacs on mac, and x11 with xterms open to various linux boxes; basically the same as when on linux. But with nicer fonts, nicer mail UA, much less administration. Granted, linux is still better by a few percent on the development tasks, but macOS compensates on the other tasks, and by its versatility. Anyways, we keep linux boxes and VMs.