Sometimes people are fast readers who make decisions about multiple choice exams quickly. Sitting and staring at the quiz isn't going to lightning-bolt me answers that I've clearly forgotten. If anything, sitting and overthinking is simply going to make me change answers that I'll later wish I hadn't changed.
Different people have different speeds. I don't get why this is such a big deal, or why people actually think that fast quiztakers are showing a "lack of respect for the class", lol. By that logic, nobody should turn in their quiz until you guys [not necessarily the poster I quoted, but the others above, including the original poster] say that it's been "enough time to show proper respect". Really strange perspective on things.