It does make sense. If you can't demonstrate that you're ready for higher education, then it's just a waste of time going to university (or even college).
And what's that about educational streaming? I didn't do too well in highschool (was more interested in computers and playing the guitar). After "gratuating" I spent a year or two doing silly jobs, then I got tired of i and a few exam for the subjects i had ignored in highschool, but needed to get admitted to the universities. Also, I took something which I think is might be a bit like the US SAT (and got high scores) to make sure I would be admitted, while other people had extra going-to-uni-points due to work experience. No streamlining there.
It's much worse in countries where you have to pay to get an education, which means that there are young people who can't afford going to university (or college) even though they might be better suited for it than their dumb but rich neighbours,