Because that would imply I had the capacity to change my future behavior based on those experiences. In reality, I had already faced consequences for late work and poor attention detail many times over my school career. Actually, that happened in nearly every grade and class I'd ever taken. But I was a good test taker and preferred to read in class rather than talk, so nobody bothered to evaluate me for ADHD. No amount of facing consequences for your mistakes will suddenly make ADHD go away. And if your home life is chaotic and unsupportive, you're not going to just be able to develop sufficient coping mechanisms on your own to function on par with expectations, even if you have strengths in other areas.

But those experiences did teach me a little something. They taught me to be grateful that most teachers are decent, forgiving individuals with policies for partial credit when you're late, because they'd rather see you engaged in learning than discourage you from even trying to finish the assignment. These days schools mostly aren't allowed to dish out straight 0s that can't be improved. And FWIW, nearly all of my college courses had policies for partial credit too.

Now I actually have ways to manage my natural executive functioning deficits, so I'm better at that kind of stuff.