People don't seem to understand that macOS and iOS were designed with two different paradigms in mind. macOS also has had to over its lifetime compete with other desktop/laptop OSs like DOS, Windows, Linux, etc., so limiting the ability to install anything did not make sense. Not saying that's exactly why, but likely a factor. They probably didn't even have an idea of an App Store back then. They didn't even have the App Store when the iPhone first launched. Steve Jobs thought the future would be web apps through Safari, so we're even lucky to have an App Store at all. They released the App Store about a year or so later after the iPhone. Apple had no obligation at that time to open up their product at all, and they still have no obligation to do so today. If they licensed iOS to other hardware vendors like Google does with Android, there would definitely be more of a case here, but that's not the case. The only license is to the end user that purchases the device.