Clutter objects like Tin Cans are far from useless, without clutter, everything would feel very sterile.
I agree, not everything needs to serve a specific gameplay purpose to have a reason to be in the game. If that were the case, we might as well just have the locations in the game consist of blank white walls with only objects that are useful to the player being placed in the environment. Without a good amount of clutter, the game world feels a lot less believable. Things like plates, forks, bowls, bones, candles, and other such items just help to make the game world feel more like it's an actual place, rather than just a place that exists only to provide players with a place to kill monsters and do quests in. I mean, that might be what the game world is, but if you can make it feel like an actual place, players are likely to like it more.