Tbh, it's not a case about scavenging for marks.
I think most people, no matter how clever they are, ask for remarks because they genuinely believe that they were capable of the next grade and also because they revised enough and answered the questions pretty much perfectly.
People predicted A*s, but ending up getting As/Bs or even Cs in some cases, is slightly dodgy to say the least, especially if they answered every single question just the way it was supposed to be answered and couldn't see a mark lost anywhere.