Well, when it was first recorded it was just a home demo, and low-quality at that. Then the three remaining Beatles at the time of the Anthology recording overdubbed another piano, and then the tape was sped up. That might explain it.
Make 'em laugh, make 'em cry
Make 'em dance in the aisles
Make 'em pay, make 'em stay
Make 'em feel okay
I'm certainly guilty at times of being lazy.