A typical use case that I imagine will be something as follows:
```php
'initializers' => array(
    'My\Service\FooAwareInterface' => function($instance, $sm) {
        $instance->setFoo($sm->get('FooService'));
    },
    'MyService' => function($myService, $sm) {
        $myService->foo = 'bar';
    },
),
```
So for some "quick" inits of a service and for avoiding that repetitive `instanceof` check.