Maybe it was best for Syd Barrett to leave the band. Some reports I have read suggest he wasn't the recluse he has painted out to be and in his later years lived a more normal life. Perhaps the rock and roll live of the late sixties wasn't for him. Sure the youth, the drugs, his mental state probably played to his demise as a guitarist.
What if he would have stayed on with Pink Floyd? How different would they have been? Barrett was a songwriter and contributor in the beginning, then the songwriting fell on Roger Waters. Would there have been more conflicts in Pink Floyd? Would Floyd have broken up sooner? Know one really knows.
We do know he influenced "Shine on You Crazy Diamond" and influenced the characters in "The Wall."