It’s because DevOps need to be able to do anything, and there are some tasks where a Mac has better software. Also, iPhones have amazing integration with Macs. From copy/paste as if they were the same device to being able to open a dev tools inspector on your computer to debug a page loaded up on your phone to just not even needing to use a phone at all (you can run iPhone apps and websites, on every hardware size and operating system version, on a Mac).