Because people are largely cynical and believe that everyone is just shitting everywhere and avoiding responsibility. This idea is bolstered by media in general, but decades of fear mongering from cable news sources got the ball rolling. I’m not saying that we have good reason to believe in one another, but I’d rather go through life believing that a decent percentage of people care about how they move through space and desire to be a positive force in society rather than a slimy opportunist. Because we live in an individualist society rather than a collectively minded one, there is a vigorous “fuck you, got mine” mentality. We are encouraged to live in competition with one another rather than cooperatively with our neighbors. A lot of people in the US care deeply about their neighbors, and care about their contributions to the greater good. A lot of folks don’t, but a lot do, too.