The McGurk effect helps explain why we like bad lip reading videos

Witness the McGurk effect, discovered when psychologist Harry McGurk thought he heard “da” after watching a video in which the sound “ba” was dubbed over a girl’s lips saying “ga.”

Forty years later, scientists have demonstrated this effect in thousands of studies, in infants and adults, in different languages, in cases where the genders of the voice and mouth don’t match and even in cases when a person touches, instead of watches, a moving mouth. But the McGurk effect is also limited. If you close your eyes and just listen, you’ll hear “ba,” and if you watch the lips silently, you’ll hear “ga.” If you reverse the dub, you don’t integrate the sounds either. The effect accompanies only certain syllables.

Basically, it's part of why we enjoy bad lip-reading videos.