From my experience in having a system installed in 1989 we only had to have one of those outside "candy cane" vent pipes installed if the system was above our basement bathroom.
Since I am on a hill everything (including the basement bathroom) easily flows downhill, so an outside "candy cane" pipe was not needed.
I agree that all those outside candy cane vent pipes should be painted in either dark green or black to better blend in with the landscaping. Actually, I believe they make those PVC pipes in black (as well as white).
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