I think you should basically say "oh by the way I am using AJAX", whether that means using Angular-style DI or require or a mixin some other means. In a language with a built-in concept of modules, you'd have to import or include something like that, wouldn't you?

There are some practical benefits, aside from the general happiness provided by namespacing. Not that every single app needs this, but it's pretty handy for example to be able to substitute a mock AJAX service for testing and offline development purposes.