Absent-minded Professor

So when I was a kid I always wondered how professors got the stereotypical absentminded adjective stuck to their name. I mean, these are the people who solve world hunger, find the cure for AIDS and build structures hundreds of meters into thin air.
Well I'll tell you. They get that stereotype because they are in fact, absent-minded. And what's funny is, they know it too! Take for example an email I received from the director of my department and god-like professor of structural geology. I had asked him for a recommendation letter and this was part of the email he sent back.
It would also be good if you could send me a reminder a few days before the deadline, as (needless to say) I tend to be absent minded.
You can't make this stuff up. One would think with all of the amazing science they do, proposals they write, strokes of genius and otherwise all around awesomeness, they could remember menial things like writing a letter of recommendation. Or for example how time works.
Another professor near and dear to my heart, (also my current adviser) told our class that for each 50 minute class period: 8 students would be giving their 5 minute presentations with 2-3 minutes afterward for questions. Anyone care to do the math on that one? 7-8 minutes X 8 students = 56 - 64 minutes total! See anything missing here? Oh that's right. Time. Time is missing here. So I gently ask him if that is in fact what he meant. Later, the class receives this email in what I'll assume is a response to my question.

Plan on:
1. coming early to class to get your PPTs loaded
2. having the class run a little longer than usual (~6 - 6:15 pm)
Everyone please be courteous and supportive and stay in class until all presentations are completed.

Does he not realize that people have obligations that don't revolve around him and his class? Obviously not. Lucky for him, for the moment, mine does.

So I've come to the conclusion that Professors perpetuate the stigma if only to protect their own little butts when they make mistakes. Forgiving them based on a characteristic they can't control seems like the kindly and respectful thing to do. If only all naive college students knew how professors take advantage of their naivety.