You’ve hit on one of the caveats of this debate. At surface level, multi-family housing looks like a recycling goldmine and much more profitable than single-family residential. But in practice, it’s not that simple. The main reason is it’s much harder to police recyclables from multi-family buildings. Everything’s going into one big pile, so if someone is consistently contaminating the valuable material with non-recyclable trash, it’s harder to figure out who. All it takes is a little bit of food or other contaminants to ruin a batch of recyclables (depending on the material), negating its value.