Sure great. You can get traffic volume from them I guess (I'll accept your word for it). But my point is that there are only really two roads between those points (connectors and frontages not withstanding) unless someone is going totally off the beaten path on logging roads which is a whole different level of planning (just look at the matrix in that area) so the average tourist planning a route will pick one or the other. And most will want to know a little bit about conditions and what you will see/encounter along the way. I get most of that initial info from GM and then, if I decide that is the area I want to tour I can pursue more info from other sources like the one you indicate. Even with google I can zoom in and use street view to tell which of the two probably gets more traffic but also what each road condition looks like. That also influences my decisions.

It's not that I don't think one should look at other sources but for initial route finding/research GM is hard to beat.