They are easy to replace with nothing though. I think it's worth it.
What about for instance book covers? They are definitely not something you can usually have under a free licence. But fair use probably applies (since the cover isn't the book itself).
Sure we could just not put'em. But sometimes they make the article on said book nicer, and may illustrate, in case of comics, stuff like that, what it looks like. Which is definitely something adding value to the article, imo.
Nicolas