The only medication I have ever taken regularly are pills for cholesterol. Actually, my bad fat levels are great but I am low on the good fats, the mono- and poly-unsaturated fats I think. I don't think my Doctor was very impressed with me when she explained this all out to me, sat there waiting for my reply with her usual stern look and then I replied "Whoohoo! More Peanuts!!"

In any case, it took me forever to get into the routine of taking a daily pill. Not because I don't value their worth or I don't value the advice of my doctor, I am simply a horribly forgetful person. Plus, they are supposed to be taken before bed as the body produces the enzymes or something or other that I am low on while you sleep. Quiet often, I stay up too late and I barely make it to the bed, much less remember to take a pill. Now that I am in the routine, it's more second nature but it took me months to become good at it.

Short version, not everybody lacks comprehension. Some of us just suck at breaking routines.
With great power comes Awesome irresponsibility.