There are a lot of reasons why normies might be against suicide, but the simplest answer is that they're not. For most people, their entire lives are about image. If the consensus says that suicide is bad, then they'll publicly agree.
Christian morality. Most identify as progressive humanitarian agnostics or atheists, but that is really just Christianity without God and strict commandments.
This is high IQ. I've often thought that there is very little difference between the moral standards of most people, regardless of whether or not they believe in a deity. Opposition to suicide is a perfect example of position that is illogical, I can at least understand why many theists make this mistake, but atheists have no excuse.
The chief failing of humanism (although there are many), is the lack of a well defined explanation regarding the belief that human life has intrinsic value. The notion that even if a person is in the worst circumstances imaginable, that consciousness somehow produces value solely by it's own existence. Which makes no sense tbh, and I could go on forever about why this belief is clearly mistaken, but I'm not going to turn this page into a pointless wall of text. How can anyone claim to be concerned about the welfare of others if they refuse to try and honestly assess the condition of human life?
Of course the response would probably be something akin to calling me a pessimist, or perhaps even suggesting that I'm mentally ill and that I can't see the world clearly. However if we look at it from an evolutionary perspective, who do you suspect would survive, someone with an optimistic view of existence, or another human with a pessimistic outlook? Obviously the answer is the former, for a whole host of reasons. Higher birth rates, lower suicide rates, stronger drives to achieve personal success, and this is just off the top of my head of stuff we'd expect to see from optimists as opposed to pessimists. Following from this, it stands to reason that individuals and communities who had views similar to my own likely wouldn't have survived, and thus whatever traits led to their view of reality wouldn't be selected for.
So if anything, humans are naturally inclined to exhibit an irrational level of optimism which increases their chances of survival. Even if I am "depressed" and this has affected my reasoning at all, it's probably made me more rational, not less.
