My ideas:
- Apple is just a few years behind; they launched a decade later. Come back in 3 years and they'll be close to parity.
- Apple only needs Maps to be good enough to avoid PR disaster, since they need a reasonable default on iOS. On the other hand Google needs to be good enough to beat competitors since they want to make money on traffic, usage data, and the Maps API.
- Google's use of reCAPTCHA gives it a huge edge over competitors in mass image classification.