You are thinking about a future world in which people are exclusively using PHP 5.4+ or PHP 5.5+. The reason you implemented the MapIterator and FilterIterator classes in Guzzle is because, while PHP does have an idiomatic way of decorating iterators, there are no iterators in PHP 5.3 worth using to decorate with to get this behavior. I thought it would be a nice little addon to expose the usefulness of those iterator classes without having to find and import them. Not an altogether important feature, so if you want to object, I'll remove it.