I don’t think the issue rests so much with caring about the pleasure of others so much as causing the pain of others. Increasing the pain of someone else has the potential of causing pain to yourself, and any egoist knows that it is in his interests to have some concern for the pleasure of others.
As far as the meaning of life and the “42” joke, has anyone ever thought about the mathematical implications of the question and answer to life, the universe, and everything? (I mean, if you ever took it seriously enough to consider it a real question and answer.) The question (spoiler ahead) is “What do you get if you multiply six by nine?” Imagine having to transform one’s entire views of the universe and perception because of one mathematical fallacy. If that were correct, a new mathematical theory would emerge that would alter the way we calculate things. Our ideas based on scientific calculations using the old mathematical theories would change. It would alter our ways of construction, of logic, and of other institutions based on mathematical accuracy because there would be a new and more correct function of all these factors.
But then again, it’s just a book.