Because of Liverpool. Before the Beatles, nothing was taking seriously unless it was London/Home Counties: geography was all and accent was everything. BBC presenters wore formal wear in the evening even though they couldn't be seen on the radio. The social barrier to the Beatles was huge: re-buff after re-buff. But once they had broken through, the world loved the wit, the accent, the devil-may-care attitude.
The world even went to Liverpool and begun to understand how it was such a strong city even though (partly because?) much was turned to wasteland during WW II. They visited the Cavern, crossed the Mersey on a ferry and did a Magical Mystery Tour. And just couldn't believe how small George's child-hood home was.
Yeah, yeah yeah: Liverpool.
It's another reason we love The Beatles.
Reason 1: Story-tellers
Reason 2: Sgt. Pepper
Reason 3: Eternally optimistic
Reason 4: Still cool
Reason 5: George Harrison.
Reason 6: Love Me Do
Reason 7: Work Ethic
Reason 8: Synchronicity
Reason 9: The Roof-top Concert
Reason 10: Candlestick Park
Reason 11: Lennon & McCartney
Reason 12: I Saw Her Standing There