Well of course on that premis there is no point in doing anything.
I guess the reason is people enjoy gaining the knowledge, or earning the money, it what drives them on.
I must say though on a personal level I have always been a bit of a "glass half empty" person and have often had feelings like in your original question, a sort of "whats the point".
I know Kenneth Willimans, the comedy actor, struggled with ill health in his later years, and the last entry in his diary is "oh - what's the bl**dy point".
http://www.findadeath...s/kennethwilliams.htm