|The Beatles play Shea Stadium in biggest concert ever, 1965|
1. Poor sound quality
The unprecedented demand for Beatles' concert tickets meant that promoters wanted to use the biggest venues available. In most cities used the only auditoriums physically capable of accommodating tens of thousands of fans were sports stadiums. Unfortunately, this created major sound problems as amplification technology was not yet ready to fill these vast spaces. In many cases the (distorted) sound came through the stadium's PA system and was a sonic mess. It was also incapable of competing with the incessant screaming.
On stage The Beatles were reliant on their own puny amplifiers. Crucially they could not hear each other play. Ringo Starr could only keep the beat by watching the gyrating rear ends of his fellow band mates. John Lennon later described how this adversely affected their musicianship:
In 2016 Giles Martin (son of George) remastered tapes from the 1965 tour for the soundtrack of the new documentary 'Eight Days a Week'. The sound is far superior to that heard by fans at the time - or indeed by The Beatles themselves. As Paul McCartney has said,
"We couldn’t hear ourselves when we were live, as there was so much screaming going on."2. Beatlemania
By 1965 The Beatles were exhausted by nearly three years of relentless Beatlemania. Elation at their initial success had soured as they faced night after night of screaming 'I Want to Hold Your Hand' over the screams of teenage fans.
Increasing, playing live became a chore rather than a challenge. Little thought was given to preparation and they hated rehearsing ('we were grown men!' as Lennon would grandly complain later).
The Beatles became increasingly self-conscious about their sloppy playing - aware that their famous performance on the Ed Sullivan was pretty dreadful, for example. They also knew, however, that most of the girls who attended their concerts were not there for the musicianship. There was little incentive for them to put in the work necessary to improve.
Live concerts were also becoming more dangerous. Security at the big concerts was often chaotic and the 'bigger than Jesus' controversy made touring the US tense increasingly tense. A particularly unpleasant experience in the Philippines heightened this sense of vulnerability.
4. FrustrationIn 1966 The Beatles retreated to the recording studio. Their retirement was reflected in new material which was beyond what it was then possible to perform live. For 'She's Leaving Home' they would have needed an orchestra for 'Tomorrow Never Knows' tape machines and engineers to work them.
The Beatles were becoming increasingly embarrassed by the poor musical standard of the stadium concerts. They knew they were a pale shadow of the band that had thrilled audiences at the Star Club and the Cavern.
The Beatles Teaching Pack (3.99)