Deep in large cities (New York, San Francisco, etc) with all the RF reflections can actually be quite challenging for GPS. Challenging == actually terrible and everyone knows it. Off by blocks, and definitely no help at all for vertical location.

And inaccuracy at start-up is also surprisingly challenging; think a person requesting a car within 5 seconds of opening the app, before the location service of the device has really resolved the location, thus ending up with a pick-up pin that is a hundred feet wrong or more. And maybe on the wrong side of a street, fence, etc.

There's also issues like Australia, which because of plate tectonics the maps corresponding to GPS coordinates had to recently be moved close to a meter.

We think of GPS as just the positioning part, but its just as important to remember that there is a large amount of work to translate that position into a meaningful data point within each given country. Just knowing someones exact GPS coordinates isn't helpful.

Have you ever used Google Maps in a country like Costa Rica? Because the country isn't mapped to nearly the same degree (also, they have a habit of not even naming their roads), it becomes barely useful. I'm not talking about the technology of global positioning, I'm referring to all of what we take for granted with it for.