Can we get back to just the basics? Why do we have primary streets in the first place? What is their purpose? Is their purpose just to make roads visible or is that just a side effect? Is their purpose to help people navigate and/or find the best routes from point A to point B? Is their purpose to solve routing problems? If so, is that meant as a temporary solution until the routing gets better, or as a permanent classification even if it's no longer necessary for routing? Is there another main purpose for them? Ignore all roads under discussion here and just think about primary streets in general.
EDIT:
In addition to the basic questions above, take a look at this road. It is a far more direct (and faster) route if you were to drive this direction. With the longer route marked as primary, Waze is likely to route you the longer way instead of the shorter way. If no route is primary, Waze will route you the more direct route (assuming no traffic problems). This is part of the issue with "randomly" placing primary streets as you end up telling Waze to route a certain way that may not be the best route.
Note also that there are other problems in that area that could have been fixed instead of worrying about the street type, but which were just left.
EDIT:
In addition to the basic questions above, take a look at this road. It is a far more direct (and faster) route if you were to drive this direction. With the longer route marked as primary, Waze is likely to route you the longer way instead of the shorter way. If no route is primary, Waze will route you the more direct route (assuming no traffic problems). This is part of the issue with "randomly" placing primary streets as you end up telling Waze to route a certain way that may not be the best route.
Note also that there are other problems in that area that could have been fixed instead of worrying about the street type, but which were just left.
Re: Primary Street Discussion