Research, with 'unusual' icons, shows that some icons are more confusing than others. Specifically, icons that have too few or too many details. Now you could argue that a certain amount of detail has become the culturally entrenched norm and that such research still doesn't prove a thing, but then the burden of proof shifts to you, to back that statement up with an experiment. After all, it also simply makes sense: with too few details, you need to choose from all possible details you could add to make sense out of the symbol. On the other hand, with too many details, you need to choose from all possible details you could remove, before the main point stands out. You're just trying to minimize the amount people have to think.