It just seems like the lesser of the evils. The process I'm hoping will kick up less SI than say hanging, jumping, train. It also depends if you're concerned about breaking the law. I don't fancy a criminal record trying to obtain Class A drugs. It can be done at home, in private. With any luck, it will involve discomfort rather than excruciating pain and fear.
Really though- all homegrown methods can fail. They all have their problems. I agree that SN likely isn't the magic powder it sometimes seems to be worshipped as. What method is though? My friend said she watched a video of an assisted suicide once which didn't even look entirely peaceful! The man struggled to drink the solution (Nembutal pressumably) and said it tasted foul and burned his throat.
Even executions have gone wrong and they're supposed to be professionals. The depressing thing (for suicidal people anyway) is that I don't think the human body is always that easy to kill. Some of it seems to be down to luck.
I do understand why people question just why SN seems to be so favoured but I'm always curious to know- what do you think sounds better? What method do you know that never fails and never has complications if it does fail? Ultimately, we're trying to shut down our bodies bit by bit. I imagine, any process that fails in doing that or, is interupted will leave us maimed rather than dead. For me, SN is simply the best out of a bad bunch.