I've read that other cultures in times past didn't look on suicide so negatively? Geeks and Romans come to mind. Many years ago, that is. I guess Rome isn't around, and I don't know, but I would guess Greeks frown on it now? I suppose we have the Christians to thank?
We have government and politics to thank... well, mostly. Also people in general being generally shit.
Once upon a time, there may or may not have been a Jewish guy in the Middle East named "Jesus", who may or may not have done some notable things, may or may not have had some relationship with a supernatural force that may or may not exist, referred to as Yaweh/God/Allah. He may or may not have inspired contemporary disciples who may or may not have spread his message and passed it down through the generations, but we know for sure that about a couple hundred years after Jesus may or may not have died, written records of his exploits began circulating. For various reasons, one of the Roman Empire's leaders converted to a particular version of the belief system based on Jesus' teachings and exploits (which again, may or may not have taken place), and deemed it the official religion of the Roman Empire. This created a bunch of problems, most importantly that Christianity was viewed as (and probably was) something of a death cult. Life being shit, and Christianity promising a fabulous afterlife, Christians tended to have serious death wishes and rush off to get themselves martyred in spreading their faith to people who didn't want it, or otherwise get killed and suiciding and so on to ditch shitty life for euphoric heaven. Because it was the official religion of the world's largest, most powerful empire (and was enforced by the government at penalty of death), Christianity spread and became a major religion.
A large number of powerful people back in the day essentially owned other people, made their wealth and owed their lifestyle (and even their very lives) to the labor and taxes extracted from lowly plebes and peasants and serfs... so having them rush off to die was a bit of a problem for political and religious leaders. If all the serfs did that, then the leaders would have to till fields and such, rather than just sending their thugs out to extract taxes. And, really, *any* piece of human property destroying itself weakened the leader who basically owned that self-destructed person, so a new rule was proclaimed that suicide was a mortal sin that kept people from getting to heaven... and also, anyone who committed suicide who have his property forfeited to the king, have his or her family made homeless and so on. This created a very anti-suicide tradition that lasted many centuries in areas with strong Christian influences, which eventually was most of the world thanks to European colonialism and empire building.
That's basically the history of how suicide came to be regarded as evil in most of the world, to this day. (Though, for the record, since the suicide ban does not come from the holy book of the Christians, there's always been a minority of Christians who believes differently, and these days, even the Catholic Church, which originated this idea so many centuries ago is changing it's views, albeit slowly.)
However, before we blame this on Christians or white people, we should look around the world a bit, at cultures that haven't had much (or any) contact with the Christian ethos, and while we find a larger variety of views on suicide, we also find a lot of societies that condemn suicide very strongly, including a large number that do the same things those older Christian kings and rulers did - seizing or destroying property of the person who suicides and shunning or exiling the family members. And, in these societies that have avoided Christian influence, there is a correlation between the level of the society's level of collectivism and how suicide is viewed - the highly collectivist/communal societies (where most things are "community property") tend to treat suicide very harshly, while the more individualistic societies tend to be more accepting, or at least less punitive about it.
Which all suggests that a society's stance on suicide has more to do with whether people are viewed as individuals, or as owned/part owned by the community or a ruler/leader. As I said at the top, because in general, people are generally shit, a lot of them feel entitled to have a say in the lives of others, if not some degree of ownership stake.