One of the biggest changes to general human thought is the measure of the worth of a human life. In a world where people are more literally irreplaceable commodities than in times past, the loss of even a single life is keenly felt. There are still several billion humans running around, of course, it’s not like there’s a shortage. Not yet. But those several billion are all there will ever be now. For that reason, the taking of a human life is considered particularly reprehensible and extreme in most cases.
It still happens of course. People come into conflict and some of them die. It’s less common now partly because of the prevailing attitude about it and partly because generally it’s more common and accepted to send robots and drones into harm’s way, a factor that tends to come up repeatedly in the conflicts of mega-corporations and ‘powered’ individuals.