I just can't see that there was no particular reason. I'm NOT saying that I disrespect Ringo. I do respect him. I like his drumming, and love the fills. I would guess that it's because he was the drummer.
Have you heard The Carefrees - We Love You Beatles on Beatles-A-Rama?
'We love you Beatles, oh yes we do...
Oh Beatles we love you...yeah, yeah, yeah'?
'We love you Paul, oh yes we do...? etc., etc. with girl screams. Sweet.