Unfortunately, that still doesn't prevent a large number of them tracking you using permissions you've granted, or permissions it doesn't need to explicitly ask for.
There have been a number of articles recently about iPhone apps phoning home regularly without user knowledge.
iOS is arguably significantly better than the alternatives, but lets not kid ourselves as to how far that trust should go.
Services like Guardian Firewall for iOS[0] wouldn't be in continued active development if the OS or review process was sufficient. Of course, there'll be plenty of snakeoil as time goes on, but at this stage, there's a lot of credibility behind the need for these services.
[0] https://guardianapp.com/