While the cases you cite are probably different, not all countries require people to actually attend a University where they get their Doctorate. E.g. here in Germany, you are required to write a Doctor's thesis (that needs to be accepted by a Professor) and pass an oral exam, but there are usually no required courses.

I think historically it was not uncommon for people to just submit a thesis, but nowadays nearly everyone getting a PhD will do so while being at the University and in close collaboration with his Doctoral advisor.