As someone who can look down from above into the recycling trucks I don't know what to make of the fact that they empty the separate collecting containers for green, brown and white glass into the back of the truck. Without any separation at all. Once I asked a driver why that is, and he answered: "I'm just the driver, no clue." The trucks are just regular "Muldenkipper / Dump Truck" which have a little crane behind the drivers cab, crane hooks into their tops, lifts them up over the back, does something to the top hook, shakes a little, bottom opens up, glass falling down, empty container back to the curb.
The answer I've always heard: because recycling facilities can't trust regular people to sort their trash right (and for good reason), so it gets dumped into one pile on the truck and then resorted properly at the facility.
Regardless whether that's the reason, I think making people sort their trash is dumb anyway, and the more requirements you give (sort into 7 piles, must be clean of grease, etc.) the dumber it gets. The effort discourages a good chunk of the population, while the rest end up wasting so much water inefficiently washing their trash in their sinks.
I mean... "Wat soll dat? / WTF?!"