I go back and forth on this one. On one hand, it does not really add anything and for a long time I did not really use it. There isn't much point without an appearance system (or a more crucial one). ...
Used in moderation it adds some character to a build and makes it feel lived in.
The problem is that many of the popular builders use so much of it all over the place it makes their builds unusable. I'm not sure who all the people who download their stuff on the gallery are, but they obviously don't use it in their games.
Also there is a curious lack of some clutter items, for example why is there only toilet roll holder?