Is it not the same for computers most of the apps data is accessible by all the apps. Mobile OS came from the paradigm of the past and as the way we use our phones change so do the way how mobile os work. For a long time Android devs have wanted to obfuscate the disk from the user like iOS does but have faced push back from users and developers so in the end they created a permission where an app needs to ask permission to access the disk.
Keeping the file system a black box or allowing user/apps to mess with it is a development question of the times dumb it down or not. Then people here complain children don't know anything about computers these days well yeah because we have dumbed it down so much in the name of security and usablity.
