I think it has more or less to do with Pop Culture Isolation.
Go to its TV Tropes page, and look at the page image: you see the question regards a certain blue video game character that's pretty easily identifiable, and yet they all got the wrong answers (lol at the lady who wrote "Dankey Kang" . . . I just love Dankey Kang, that's a great game from Tinendo).
I mean, in the case of Justin Bieber, now, I don't know what they teach kids in school today, but as far as the average young person goes today, and with how anti-book society is now, how many young people do you imagine would even be remotely familiar with a literary classic like Tom Sawyer? Heck, when the movie adaptation of THE GREAT GATSBY came out, I was surprised I never heard of it, because my reading courses during my high school years pretty much had me reading these literary treasures. Tom Sawyer? To Kill a Mockingbird? Yep, I read those.