According to Cult of Mac, Apple removed Google Maps in iOS 6 since Apple wanted Google’s turn-by-turn navigation service in Maps however Google refused. Google plans to have new Google Maps in App Store by end of this year.
It is up to you to decide if you are happy with Apple’s new map or wait for new Google Map to come soon. If you can’t wait for it by end of this year, you still can go to maps.google.com from Safari on your iPhone and add it to home screen anytime.
