Possibly because he was rather an outsider of the "scene". There's a great biography (unauthorized of course) called "Fear and Loathing" that recounts his life during the '60s... his meeting with Timothy Leary (whom he soon detested), his meetings with Kesey, and other various elements of the counterculture - none of whom he apparently got on with.

I'd consider him more a product of the Death of the Sixties rather than a product of them. At worst, his writings are a drug-addled mysoginistic violent mess. At best, it is genuinely insightful social commentary taken from an outsider's point of view, and journalism from a journalist who refuses to divorce himself from the story.

One of my favorite books of his is "Fear and Loathing on the Campaign Trail", where Rolling Stone turned him loose on the 1972 election campaign - he rapidly became disillusioned with the job (some say he went unwillingly to begin with), and soon turned on the politicians he was covering. Sublimely subversive and disturbing at points...

M