^For pollution control. That is the same reason for EGR routing exhaust gasses back to the intake. The proper method is to dump the oil back to the sump or collect it in your used oil containers for proper disposal. Imagine if all vehicles would do the same dumping in the road, well end up with oiley pavement just like in the early40s where its not illegal yet to vent those unburnt gasses. BTW those provent have a bung designed to route bak the oil to the sump.