The case
It's the most-parodied scene of the decade: socks, oxford shirt, Bob Seger's "Old Time Rock and Roll" on the stereo. Watch it: Cruise's eyes are uncovered the whole time.
The Wayfarers are all over the rest of the movie and on every poster, so the mind reasonably puts them on him during the dance. Every parody since has added them, which made the composite image the official one.
Why our brains do this
Two iconic images from the same film, the poster and the scene, merge into one. Parodies then reproduce the merged version.
Sources: Wikipedia — Risky Business · Wikipedia — False memory: the Mandela effect
