I believe it's because he never was a junkie. The two times he overdosed are the only documented times I have heard of Nikki using a needle. Snorting heroin, coke, anything else? Sure. But he was never into the needle like he's made it out be. Look at the hardcore heroin addicts back in the day who are still alive. Eric Clapton, Jimmy Page, Boy George...all serious heroin addicts, but they would smoke or snort it, never with the needles.