Earlier quoted context omitted.
Side streets need to support their fair share of traffic. Most cars these days are very quiet, barring the occasional beater, utility truck, and ricer. That being said, if they slow cars down Waze will direct less drivers to them.
Side streets need to support their fair share of children walking to school, bicycles, conversations and not-polluted air. Their fair share of traffic is very low, only traffic to or from a building on the street.
So do main streets.