You need root, because there are apps you want to run, that need root permissions. The use cases for these apps are very wide, from ad blocking to repairing OEM

You need root, because there are apps you want to run, that need root permissions. The use cases for these apps are very wide, from ad blocking to repairing OEM fuckups (I'm looking at you, Asus). Anyway, it is easy to "root" Windows or Mac OSX. It is just logging in as administrator in Windows or using sudo in OSX. The paranoia and preventing the user to really control the device they bought is a new thing, that came with mobile OSes. It wasn't so widespread before.