Functionality of styles

Hello, All,
I’m not sure if this topic has been covered before. If so, I apologize. (I did some searches of the topics but didn’t come up with anything relevant.) I’ve recently begun using OmniOutliner, having used several highly functional notebook programs previously. I emphasize functionality in my evaluation of programs. What exactly are the functional uses of styles? From what I can tell, one cannot search for passages that are highlighted and there is no index of such. I grant that, if one memorizes which level has which associated color, one can remember where one is in an outline. But other than that? If the styles have no practical function, are they there simply to make the outline more attractive? Or promote easier reading? If there are aspects I’m missing, I’d be very grateful to know about them.