Apparently, to summarize several responses, brevity is key. Well, I like brevity as much as the next person, but I also like explanations and arguments, and it seems that most quotes achieve conciseness at the cost of leaving out the "why". So after reading a quote, I can have one of three responses:
1 and 3 don't provide me with much benefit, and I usually don't bother to do 2, because of the hassle involved, and because I don't know whether the source material even contains an attempt to argue or explain.
A monthly thread for posting rationality-related quotes you've seen recently (or had stored in your quotesfile for ages).