Apple Maps is an unfair comparison. Like Uber it can store local map data and knows your phones location as soon as it opens. What Uber ALSO has to do is reach out to find the location of all the cars around it and start putting that data together to give a user the full experience. It would be pretty crummy if I got ~5–10 seconds into the app and requesting a ride before figuring out things like surge pricing is in effect, there are no cars around me, etc etc.