well you see when film was created it was 35mm camera.. over a 100 years ago..
the aspect for that was 4:3, and the first TVs came out like that too
Soon people everywhere fucked off the movie theater in place of home comfort cinematic viewing, and this did not sit well with (((hollywood))). They decided to royally fuck over anyone with a 4:3 screen by filming in massively wider screen formats, at first with tremendous costs, 3x at first with Cinerama
But being the big fat jews they are, they wanted to do it on the cheap. Cue anamorphic lens, which did fuckup the shot until the projector in the theater corrected it but bam, let them continue using all their 35mm equipment.
Today its little better because of kenny powers 16:9 but the movies are so shit for other reasons its not even worth worrying about letterboxing or being panned & scanned.