SN isn't perfect, but it's a hell of a lot more reliable than booze. Almost anything is. What you're talking about, acute alcohol poisoning, is totally unpredictable. Booze isn't heroin - you can't just add up potency and tolerance to get a guaranteed death. I've known people who drank themselves to death, and none of them did it intentionally. Verne Troyer (Mini-Me) pulled it off, but he was literally one of the smallest people in the world. Unless you're 2'8" tall, the odds are against you.