But most files on Linux (see e.g. /usr/share/) _are_ accessible to users, as in read only. The file manager isn't normally used for editing files, most people would use it to find and inspect files. There are lots of files on the system that would be easier to find with a file manager, for most people.

Then again most of the files outside /home/user will only be confusing to many people. But it's not really true that you would get permission denied errors just by looking at them - there are quite few of those. In any case the file manager should allow access outside of /home/user/MyDocs/.