We use the most sophisticated sorting device known.
Humans!
Of course, we're probably not as fast as a computerised sorting centre, but we're able to be very accurate, and flexible. But we're also costly, and require nuisances like lunchtime...
I suspect that rules are set, and then some rules fail to follow changes in opportunity and so on, hence everything ends up piecemeal.
Here's another example. A council

contract the removal and sorting of recyclables to a waste removal comany. The company will only deal with cardboard in big bales. The council are about to install a baler at the market place for the market traders' cardboard waste, but to fit in, and produce handleable bales, it has to be a small baler. The small bales would cost the council money to have removed, because they are smaller than the company normally deal with.
If the council give a small community recycling outfit those bales, free, they can sell them to their waste merchant, for profit, because they deal in skips of loose cardboard.
So small wins. But if we (yes, you guessed it) weren't there, being small and flexible, it would be costing the council...
We like to think of ourselves as the small mammals, running beneath the feet of the dinosaurs.