Apple and Mozilla have already stated that Pepper is entirely redundant with ongoing standardization efforts and even counterproductive to them. So why is Google pushing it? Answer for yourself.

Apple's initial third-party app system in the iPhone was web-based.

While WebOS stuck with the open technologies, the next Apple phone introduced closed-source binary application as the main third party extension platform. If WebOS could make the open web technologies work as primary development method on a phone, why did Apple go back to the installable programs of the last century?

Google's Pepper is at least open standard with an open implementation, while I don't have any way to run iOS apps on any other platform than those tightly controlled by Apple themselves.

Strangely, we can look to Microsoft for providing an open standards HTML5 based version of an app like "Cut the Rope": http://www.cuttherope.ie/ -- imagine if iOS devices ran HTML5 apps well and this game (which sold 3 million copies on iOS!) was HTML5 from the start. You could run it on the iPhone or any Android device or your desktop right from the start.