Why do so many recipes call for powdered sugar instead of regular sugar?

This is a question I've been wondering about for a while as a home baker and amateur food scientist. Why do recipes for whipped, fluffy desert components like whipped cream or buttercream icing always seem to call for powdered sugar? If I want to add sugar to a something, why would I also want to add the anti-caking agent (usually starch I think) for powdered sugar as well? Is that starch actually something beneficial for a whipped desert? Because as far as I can tell, the only time powdered sugar makes sense is when it's dusted on top of something or incorporated into a desert that is being mixed by hand and doesn't have the shear of a mixer to dissolve or emulsify the granulated sugar. And I've never had any issues just using regular granulated sugar and honestly prefer it to powdered sugar for icings, whipped cream and the like. If a recipe calls for powdered sugar, but it's being combined with a mixer or beaters I just use regular sugar and the results are great.

Anyone have any thoughts or experience as to what I'm overlooking? Or is it just a hold over from a time when electric mixers weren't common and you needed a finer sugar to incorporate the sugar by hand?