The deal is, some passengers are convinced they know the best route from point A to point B, and will accuse drivers of trying to con them if they don't take that route. So if the passenger has a route they want to take, even if the route is stupid, you just shut up and do that. Otherwise, you take the best route.
In theory, of course. I have no doubt that there exist cab drivers and Uber drivers who run up the meter. Hopefully, Uber does some monitoring of routes and catches at least egregious cases.
Basically, if your Uber driver starts using a traditional GPS instead of Google Maps, get worried. That's my experience using Uber in LA for longish trips out to Marina del Rey, anyway.
(Going the other way: "The LA convention center? Where's that?" "Right next to the Staples Center." "Do you know what streets?". I did, but really? I'm from New York and don't have a driver's license, and _I_ know how to get there...)
It seems like a flaw in the Uber app that the customer can't just provide an intersection or an address, and the driver gets immediate turn-by-turn navigation. Yes, Uber still needs to blind the driver to destination until pickup, but it's not a huge obstacle.
The other thing is that users just HATE typing in addresses on smartphones. It's like the worst-case scenario for smartphone data entry -- lots of different fields, and words that are not in the dictionary/don't autocorrect well. So Uber (and Lyft, and (ahem) Flywheel (which I work for)) do not require that a user input a destination.
That's why I don't like the preferred route question. Do I want to pay more for a longer trip? No.