Well obviously--
Android is open-source software. Google even encourages programming it, hell, they give you, for free, a program to gain root access into the adb shell:
Android SDK | Android Developers
The iPhone OS however is not, no third party apps, nada, Apple wants complete control making it much more difficult to gain root access. This development, from an objective standpoint, is definitely something Apple did not want to happen evidenced through the obvious fact that the iPhone OS is markedly closed-source.