There's actually no shortage of B side tracks that went on to became of the most famous, favorite and popular songs in rock history. Sometimes even eclipsing the A side. [1][2][3]

Everything from Elis "Hound Dog", The Smiths "How Soon is Now" to Zeppelin's "Hey Hey What can I do." B-sides are/were often a chance for an artist to release something the record company rejected for the album but the artist really wanted to release. B-sides are actually often things for the fans.

[1] https://ultimateclassicrock.com/b-side-big-hits/

[2] https://www.yardbarker.com/entertainment/articles/25_of_the_...

[3] https://www.radiox.co.uk/features/x-lists/b-sides-more-famou...

As a counterpoint, here are the B-sides from that British quartet of yesteryear, most of which were only released as singles (until the discographies were published decades later). Some of these are better than the A-sides. YMMV.

P.S. I Love You, Ask Me Why, Thank You Girl, I'll Get You, This Boy, You Can't Do That, Things We Said Today, She's a Woman, Yes It Is, I'm Down, Day Tripper, Rain, Yellow Submarine, Penny Lane, Baby You're A Rich Man, I Am the Walrus, The Inner Light, Revolution, Don't Let Me Down, Old Brown Shoe, Come Together, You Know My Name