For one, you learn faster. Secondly, there's a chance someone else was thinking the same question and was too afraid of looking "dumb" to ask it. Just make sure you don't occupy all of their time with questions, especially in a public forum, thereby wasting other peoples' time.
The quote was actually talking more towards speaking up in an attempt to impress the expert with the little bit of knowledge you have in the subject. It's patronizing and they often see right through your front. It is much more effective to let the expert do their thing and for you to learn than trying to impress them with your little bit of subject matter knowledge.