A lot of good stuff here.
I am guilty of adding references, but I don't think it's an ego thing... I do it because I think it adds a certain level of detail and life to the story. Like seeing a poster for a band or a movie in a scene in a film. It makes it more real. It also makes it more real because when people have conversations they reference all kinds of pop-culture (this is a very Whedonian way of doing things, I probably get it from him). Of course the pop-culture I will reference will be pop-culture I'm familiar with. I will, especially, mention real bands and artists, because music tends to be important to my characters. That also means it isn't idle, it's plot-related, because it tells you something about the character.
I think most of these clichés can be justified if they're done well and if you know what you're doing and are aware that they are clichés, so that you can do them differently. Just like how, once you know and are aware of all the "rules" of an art form, be it music, painting or writing, you can safely bend them to breaking point and use it to create good art.