When you create a custom renderer, default PageRenderer.ViewDidLoad implementation creates a gesture recognizer. This gesture recogniser prevents over views (that you add in your custom recognizer) to receive touch events.
For example, if you add a UIToolbar to the view you can't handle UIBarButtonItem Clicked events. As gesture recognizer is added behind the scenes someone can spend hours (my case) to figure out what's going on.
Why is it required to add this gesture recogniser and why does it prevent touch events for subviews?