The way in which the iOS closes applications.
When I first picked up an iPhone (iPhone 7). It took me the longest time to figure out how to close applications and to view all the applications that are currently running. I mean I figured there would be an exit option in applications, but to have to double tap the home button(I thought it was only a fingerprint scanner at first) Then instead of having the same option to clear with notifications to the left then click clear but to swipe up? I have been using an iPhone and iPad for a while now and I still do not understand why Apple does it this way. I put it in the category of how you have to mount a virtual drive to install an application on OSX. Does anyone know the backstory as to when and why the process of closing applications and dismissing on screen memos is so awkward?
(Edit: I am asking for an understanding of their design principles and why they do what they do, not a debate, because if you ask me a terminal is better anyway but unfortunately not too many programs run out of a terminal nowadays.)