Why this in onDeviceReady is not this as usual?

Why this in onDeviceReady is not this as usual?

Below code is from index.js generated by PhoneGap 3.0, my question is why
it was not designed to allow us to use this.receivedEvent as usual (and
get event object as a parameter).
// The scope of 'this' is the event. In order to call the 'receivedEvent'
// function, we must explicity call 'app.receivedEvent(...);'
onDeviceReady: function() {
app.receivedEvent('deviceready');
},
Thanks,