Why does removeEventListener need a callback?

Neither way you mention works.

To remove event listener you need pass function reference or event listener id to "removeEventListener" function.

If you add anonymous function, like this:

myView.addEventListener('click', function() {} );

you can't remove that event listener because you don't have function reference. Because of that, you need to store it to some variable:

var eventListener = function() {};
myView.addEventListener('click',  eventListener);
 
//now you can remove it
myView.removeEventListener('click',  eventListener);

You need function reference because events can have multiple event listeners attached and that's the only way you can distinguish different event listeners attached for same event. Documentation is misleading, "callback" is not callback in right sense of that word, "callback" in documentation should be function reference passed to the "addEventListener" function.

Other way is to store event listener id. I'm not sure how this is done, this is not mentioned in the docs(!), but it can be found in JIRA (search if you're interested).

I think this is how it's done:

var eventId = myView.addEventListener('click', function() {} );
 
//removing
myView.removeEventListener('click', eventId);
//or this
myView.removeEventListener(eventId);