It’s more that there is far more protecting the system (and also e.g. data from different apps against each other, or things like access to your screen content)

It’s more that there is far more protecting the system (and also e.g. data from different apps against each other, or things like access to your screen content), than the current user. Some of this is because we’re in a world where Macs and iPhones are far more likely to be single user machines than the UNIX machines of lore. See the PDF in my other answer.