You only hear about it when it goes wrong.. Makes sense people think it fails more often than not.
There is a lot of factors in this method and things can fail. SN is my chosen method for the day I will leave, I am only missing the SN. I don't dare though to have it around in case I eat it without following a proper guide. I think some of the failed attempts happens this way.
Well, it's always a good idea to remember that we're unlikely to get a message with thumbs up and something like "that went smooth, I'm dead now, 10/10 recommended"

Still I guess when we don't have solid data (from hospitals/morgues etc.) it's all anecdotal evidence. I see no reason for people to preach either for or against SN, either you use it or not, but why preach against it or for it? The risk of serious harm like brain damage is unlikely, and risk of disfigurement non-existent, so it has a huge advantage against hanging or gunshot. That is what we know. Failed vs. succeeded attempts? We don't. People have been hanging themselves for millennia, and blowing off their brains with guns for centuries, and the SN idea is fairly new. Humanity also has a plenty of not-very-humane experience in hanging convicts, so we quite a lot about the method - enough to think twice before attempting it, but usually if a human with a brain that isn't already too damaged learning something about a thing like this makes one think twice before trying it

I mean I guess all of us would prefer to be put down with N, an act of mercy that is allowed even to pets, but well, here we are.
The lack of medical/scientific literacy or any kind of literacy in humans isn't of course my reason to ctb, but it kinda doesn't make me too enthusiastic about existing. Sometimes reading this forum I feel like we'd see failed attempts even if there were ikea-style instruction manuals provided with every item that could be used for that. And that if the informed consent would be the only thing required before being euthanized, no questions asked, plenty of people would not use it despite of wanting to die, because they would refuse to get informed. Like providing them with a simple test to make sure that they understand their informed consent form would be a stricter form of gatekeeping than some pro-lifers here.
Our species, 1/10, not recommended. Sorry for my rant.