Me too. You just unzip your pants fly, pull down your underwear waistband, and pee.
When I was a kid, nobody used the ‘fly’ in the underpants. (We didn’t call it that; we didn’t even know it had a name.) We were all ‘wtf is that for, and why would anybody use it to pee through?’ Our consensus was that it was an excuse to put an extra layer of fabric front and center to catch the occasional drip.
You’d have to pull both of those layers of fabric out of the way, one from each side, to pee through the opening - much easier to hook a thumb through the waistband and pull down.