As a physicist, one of the first things we learn is that physics never answers "why" questions. Nonetheless, people do ask perfectly reasonable questions that are phrased as "why" questions -- "Why is the sky blue?", for example. What they mean, of course, is: "how/by what mechanism does such and such happen". Where does one go to get his "why" questions answered? The stock physicist answer is "religion"; by which physicists actually mean to say that asking why is meaningless, so feel free to shop around for any answer you like. Prayer seems like such an integral part of religion that one may never think to ask, "why pray?" (Besides, obviously, the anti-religious crowd who aren't asking at all, but are making a snide commentary on the entire institution.) I have learned a lot, though, by asking questions no one thought to ask. So... why pray? To make the question more concrete, imagine I were to walk ...
This is a paraphrase of the pasuk in t'hillim 84:7 -- "mei'chayil el chayil" -- which means "from strength to strength". In this case, it is my thoughts and ideas to those who are strong enough to be interested :)