The reason Apple cares so much more about iOS than MacOS is vastly increased control. With iOS, they control the hardware from the chips up, the OS, which apps you can run, and via Safari-only access to the internet, even what you can and can't do using external services.
It makes computing & communications an Apple theme park, where you can't bring anything forbidden into the park, have to buy everything you need from Apple concessionaires, and can't do anything that they haven't planned for you to do. The people in the "park" pay to enter and then become a new type of domesticated herd to be milked.
You can't allow people to bring heavy equipment and power tools into a theme park, but you also can't build the park's controlled features without them, so how do you give power to authorized builders while keeping it away from users? In a physical theme park, they have controlled users during the day and empowered builders at night.
But in Appleworld, I'm thinking they'll keep iOS locked down by limiting the building tools to MacOS.
A unix-style workstation that gives maximum power to its users is so antithetical to everything Apple stands for that MacOS would never be created today, but since it already exists, they can take advantage of it to make iOS even more locked down than it would have been. (And refuse to let any other company use MacOS and not port Xcode anywhere else.) You want to see what your computer is doing (file sys, CPU procs, memory, network, etc.)? Do it with a Mac. iOS is not YOUR computer. It's Apple's. You only paid for admission to iOS, and you aren't allowed behind the locked doors. If you want control, you're in the wrong place.
I'm afraid that if they ever figure out how to sandbox an iOS partition of some sort to allow builder tools to run on iOS itself in a totally controlled way, then the Mac is toast, but the Mac gives them time. I think that for the foreseeable future, they won't risk any accidental empowerment of iOS users and will limit the power tools to the Mac.