Ive tried to understand where klang is coming from when he talks about the song being somehow original structure wise but I cant see it myself, for me its a very good Beatles song, well sung that showed L & M were truly excellent song-smiths..............one thing that lets it down for me is the lyrics 'If I fell in love with you, would you promise to be true' is a tad corny (you rhyming with true has been slightly over-used).
As far as melody goes I always thought John was 'inspired' by Nat King Cole's 'When I Fall In Love' from 1956.
I would always rate Nat's song as higher quality than Johns though, both lyrically and melodically and it has become a well deserved standard.
I do love the song though, and the way they recorded it.
As far as the Beatles 'inventing' not putting singles on albums, from memory, this was never really attributed to them in the 60's, it was always described as a 'British' (money concious) thing, thats why other British bands like The Stones also didnt do it. Ive no idea when or why it was attributed to The Beatles.