Very few connectors are (look) symmetric but can't be plugged in both directions. It is actually a very big oversight by the design committee because, sadly, most of us are not as sharp as you.
Don't think of it as "designed for idiots", think of it as "reaching for the cable in the dark and trying to get your phone on the charger in the last few moments of consciousness before you fall asleep" and you'll have a better idea of why it's reversible.
There should be a cutoff point for "designed for idiots" - if you can't plug in a USB cable, you should not be touching anything electric really.