The reason that Clark's disguise is so effective has been explained time and time again in the comics. First, it's not just glasses and a hairdo change. He wears clothes that are too big, changes his posture, and raises his voice an octave. Plus, there's the biggest thing: People don't even think that Superman has a secret identity. He has the powers of (to them) a god, and he doesn't wear a mask. To most people, he's just Superman. Someone sees Clark Kent, and they don't see Superman with glasses, because they're just not looking.
^ There's no need to condescend. Fanwank comic explanations are still fanwank contrivances, and prior comics are not synonymous with Snyder's movies.
: Tell that to any celebrity - including Cavill himself - who walks down the street in NYC and is recognized multiple times per hour, if not block, but only if you don't mind being laughed at. This
is gonna fool very, very few people in any reality resembling our own.
Hey lets play a game!
It's called "Search and Find: Secret Identity Edition"
Here we have Captain America/Human Torch/Chris Evans
Face from the A Team/Rocket Raccoon/ Bradley Cooper
The Wolverine/Hugh Jackman
Rachel Dawes (from TDK)/Maggie Gyllenhaal
Oh look it's Sherlock/Khan/Benedict Cumberbatch. He must be on a case to find Moriarty.
FOUND HIM Jim Moriarty/Andrew Scott
Loki/ Tom Hiddleston
Is that the Doctor?!
Tenth Doctor/Hamlet/David Tennant
Photos of Chris Evans, Maggie Gylaanhal, Andrew Garfield, Hugh Jackman, Neil Patrick Harris taken in NYC.
Photos of Benedict Cumberbatch, David Tennant, Tom Hiddleston, Andrew Scott taken in the UK.
If you didn't know who these actors were or if you didn't take the time to look closely; you probably would not recognize them I think most people would pass by them completely unaware. Supes disguises probably works under the same principle. People don't expect to find Superman walking among us. They watch the skies hoping for a glimpse of him. No one is watching Clark suspecting he might be Superman. Just like no one suspected billionaire Bruce Wayne to be the Batman.
"PAY NO ATTENTION TO THE MAN BEHIND THE CURTAIN"