Because George Harrison was in the team. The quiet one, the one who initially was possibly held back by the splendour of the Lennon-McCartney singer-songwriter team (who wouldn't have been?). Although maybe if he hadn't have had that daily drip-feed, maybe - just maybe - those chords and lyrics would have been lost to the world. But over time and as his confidence developed he burst forth with gorgeous songs, especially when he went solo. George was the spiritual one; he took his meditations seriously. Mind expansion was music expansion.
It's another reason we love the Beatles.
Reason 1: Story-tellers
Reason 2: Sgt. Pepper
Reason 3: Eternally optimistic
Reason 4: Still cool