The PCV (Positive Crankcase Ventilation) valve extends engine life. Moisture, and other byproducts of combustion need to be pulled out of the crankcase otherwise they turn the oil acidic and produce sludge. The old "road draft" tubes worked OK if you were moving at a pretty good clip, and didn't mind breathing leaded oily vapors from the cars around you.
The PCV valve wasn't a strictly a product of the "smog era" either. Jeep has used them since the beginning in WWII.