GTD Times: Why is it so hard for human beings to get organized?

A GTD'er asked David Allen:

I have read Getting Things Done many times and am attending the Boston seminar.  I have a question:  Why is it so hard for human beings to get organized?  Why do the techniques you recommend require so much effort and encounter such resistance from human nature?  I'm not interested in this academically, but if there is some biological/psychological/historical aspect of human nature that makes it so difficult to organize, it might help us learn how to overcome them an