there's no real reason to not just use Google Maps as your goto maps app in iOS.
Luckily, the interconnection between "default apps" isn't as big with the maps app as it is with, say, the default web browser, the default email client, the default media player.
The wonky start of Apple maps made people immediately lose trust in the app. And if you end up always double checking via the google maps app anyways, why not skip the built in maps app altogether.
CarPlay, with its lack of support for Google Maps, is why I continue to hope Apple Maps improves. I think I always use Google Maps when I'm using my iPhone directly.
And all this for free from both services?
There has to be a catch right? It's actually so big brother can track all cell phones more accurately right?
Generally speaking, if something is free, it's because you are the product (usually, as a target for advertising).