Depends on where you draw the the line between reasonable and unreasonable decisions. I don't see how suicide can be unreasonable, as long as it is intentional, done with purpose. Purpose, whatever it is, is a goal and suicide is a chosen way of reaching it, I think. You touch a hot pot (a hot part) and reflexively withdraw your hand. Would that be intentional action because it seems to be done with a purpose (in retrospect), or unintentional because you didn't seem to make a conscious decision (for whatever goal, presumably to avoid pain)?
Can reasoning be performed unconsciously (without you noticing it)? Or does it require acknowledgement from conscious side to be reasonable? I wish I could express myself more elaborately, but I can't get rid of a feeling that it does... I'm not into science or disciplines or whatever, feel free to correct me if you think I'm wrong. Reasonable, logical decision is made by a specific set of principles/rules/algorithms. Can these principles/rules/algorithms be stored (Let's say you know laws of logic perfectly, whatever they are. Then over the next few minutes you don't think of them, then you recall them, all at once or one by one, doesn't matter right now. How, where, in what form, in what dimension were they? That's how.) somewhere under the water (visible) level and used habitually? Think of a word "lake". What words rhyme with that word? There are whole flock of words that you may know, that you could match and ask yourself if they are rhymed. But somehow you find at least one with relative swiftness... I feel like getting off on a tangent here. Can suicide as a decision be reasonable? Depends on what goal is being set, I guess. (And maybe also, whether or not such decision is based on premises which are proven/confirmed to be true, which begs to discern what evidence is sufficient to acknowledge these premises as true, but I think it's not necessary.) If you want to die because you think you are constantly suffering, your goal is not to suffer, and you believe that death is a pathway to this goal, then yeah, sounds reasonable for me. Not always irrational.
Ok, blue toothpaste is over; I'm surfacing immediately. It's kind of amusing how questions about human behavior usually have personal interest (pain/pleasure, feel good/bad hormones included) in a background, or habitual, automatic actions, because we can't afford to question everything, so we go with status quo.
And why does society try to keep us desperately alive?
Taxes, belief in preciousness of every human life, local laws and their enforcement, experiments on living humans, exercise of power and control, religion, attachment...
Why is suicide still a completely taboo topic in society?
Challenges the notion of life as inherently valuable, cultural programming, tradition, religion. For me again seems to boil down to either concern with personal benefit, or habits, or mixed. Evolutional habits (tradition, habits passed down by survivors). Lack of mental capacity to process suicide. Our brains may be too busy surviving to allocate some free space on questioning things. As a result we resort to simplified explanations to things. Forced to choose denial over acceptance.
And why are suicidal people still treated like criminals in many countries?
Both are viewed as more harmful than beneficial. We don't like things and people that are harmful, and want to stay away from their influence. Suicidal people spread harmful thoughts, they get quarantined until they stop expressing suicidality. Probably my imagination had played out.
Does suicide prevention really lower the suicide rate?
I haven't seen the stats but I believe it does. People die from other means instead, die from medical intervention, get drugged and die from collapse of vital systems (if people feel shitty, suffer and want to die, there might be a damn good reason involved, like withering away without realizing it's not just in our heads), denied the means (info, tools, substances) of peaceful methods, denied assisted suicide for those who aren't capable of doing it themselves (the way we have with surgery, fire extinguishing, attorney services, etc.)