Everyone eventually winds up writing about themselves - the problem is finding the best way to go about it. To write about oneself literally, in the first person, presumes a more interesting personal life and philosophy than most rock lyricists possess. John Lennon was good for one great album based on musical direct address, 'Plastic Ono Band.
James Taylor is the kind of person I always thought the word 'folksinger' referred to. He writes and sings songs that are reflections of his own life, and performs in them in his own style. All of his performances are marked by an eloquent simplicity.
As a performing group, the Beatles began by playing old rock favorites, for dancing, to tough audiences in Liverpool and Hamburg. When they began writing seriously, they discovered that they couldn't compose in the early American rock tradition.