From my understanding its often because those side roads have different "weights", based on expected traffic load on the street designs and what not. Its wantin

From my understanding its often because those side roads have different "weights", based on expected traffic load on the street designs and what not. Its wanting to push you on to the main streets, often because when it gets too loose about routing people through all the side streets residents complain about the quiet side streets becoming busier than intended and things can become less safe. People don't like their normally quiet residential side streets becoming the new main street because Google decided it might save some people 2 minutes so it routed half the city through there. It definitely varies a good bit from place to place though. I'm mostly talking about comparing different routes on like 70+mi highway paths through cities around DFW, where each of these highways would have pretty much identical weights its just a question of which of the potentially hundreds of possible routes to take. There's tons of highways crisscrossing each other, for a lot of paths its not just a "hop on the interstate". Which interstate? What path do I carve to cut over? When do I decide to start going South, on US-75 or I-35E or Dallas North Tollway or President George Bush Turnpike or 820 or I-35W? Which highway do I take to go West, PGBT or I-30 or I-20 or 820 or 121 or 114 or 183? Then factor in some of these are toll roads completely, some have optional tolled express lanes, some have HOV lanes, some are toll roads for some stretches but not others. Having the navigation systems say "You can go this route, and it'll take an 1:20 but be free, or you can take this route and it'll take you an hour but cost you $5, or you can take this route and it'll take you 55 minutes but cost you $14" is pretty nice. Because sometimes that freeway path can also be 55 minutes, or maybe sometimes that $5 tollway path has an accident and will actually take you 1:30. Or maybe you do want to take that tollway for a bit but be sure to get off at that highway otherwise you'll get stuck in that traffic, or the inverse of that. And when you're talking about an hour long route, the traffic situation may change significantly while in route.