The purpose of the news isn’t to make you feel good, it’s to inform you of what’s happening outside your front door. But there’s neither time nor space to tell you everything, so some editorial work is required to distill it down to something you can reasonably absorb. Every news source has a different policy around how that is done, obviously. Good news has its audience, but it’s smaller than the one for other kinds of news. And since news costs money to gather, news outlets rely on advertising as a primary source of income. A bigger audience brings in more advertisers and more money, ergo, bad news is the way to go.