What kind of question is "Why?"
When you ask "Why do trees grow?" or "Why does the Sun shine?" what answer do you expect?
If you ask "How do trees grow?" or "How come trees grow?" we can answer that going back all the way to some point before trees existed.
Similarly, if you ask yourself "How did I choose to eat what I ate for breakfast this morning rather than choosing something else?" or "How come I chose to eat that?" you can answer that going back all the way to your primordial ancestors.
But when we ask a "Why?" question aren't we setting ourselves up for failure seeing as we've never really answered a single such question?
Also, this: http://www.imdb.com/board/bd0000130/nest/263626706