Back when the Beatles started in the 1960s (ask your parents if you don't know who they are), they were four fresh-faced young men from England with identical mop-top haircuts. It was only in later years that they started to try out new styles.
Paul McCartney, in particular, grew his hair very long during the 1970s. It was a look that he kept for the majority of the 1980s too, although he's now firmly settled into his senior years and trimmed it back.