They are trying to exclude large swathes of the population?
It is extremely common for people with ADD to focus better when they keep the part of their brain that distracts them busy. In college I folded origami in lectures so that my brain wouldn't go off on tangents that would lead to me tuning out significant sections of the lecture.
Some people combat the tangents by being busy, and some people embrace the tangents (which can be valuable for understanding) by listening to lectures multiple times.