Well, on one hand, mobile operating systems like iOS were designed to be a big step up from the security perspective; android was born more like a desktop operating system scaled down to mobile but has progressively increasing security isolating apps more and more within their sandbox with less options to run in background, hook into the general user experience of the system, and manage things that they don’t belong to them.

On the other hand, your example is wrong on macOS where apple mail and safari are sandboxed. So desktop operating systems are trying to catch up security wise and go beyond the traditional Unix security model.