You don't try to acquire the rights to filming furniture; urm, at least the kinds of furniture I'm aware of. No one gets penalised for that, but then again it's completely different from media-based content; but the important thing is, the viewers of that film isn't getting any benefits from watching those furniture be featured. While I'm a bit painfully neutral to who deserves what since I think no one deserves anything and are just being entitled bastards on things based entirely on morality (throws the legal system out the window), videogames are a mixed bag in contrast to non-interactive, viewable media.
A movie can only be watched and heard, and the audible bits usually have their own copyright laws attached to them, so there's not much to debating whether they should get credited or not since any form of feature will be sharing its content (shovels up the legal system back inside)
Now streaming video-game content in the form of Let's-plays or Walkthroughs are a bit different. After all, it could be argued that they're re-purposing content and you'll be right, but that's also debatable. After all, they're not selling the interaction, which makes a videogame by its definition a "videogame", but rather the audible and viewable contents as well as their own work either by playing the game or putting on a show.
Some people watch Let's Plays for the videogames, but most people actually watch Let's Plays for the reactions and effort the streamer produces. Because videogames are a bunch of other forms of media combined, I don't believe a one-size-fits-all form of copyright law is the right way to go, which suggests the problem lies with the laws themselves and videogames are rather a bunch of copyright laws than just a single entity. There are so many grey areas it hurts, and you know what, at least lawyers have something to play with.
Also if feel Youtube, in their quest of having people make money off their content and efforts should have a means of allowing their users easy-access to request permission for any form of media. But this also doesn't seem like an easy thing to do.