Comparing is often viewed as negative because people often compare the best things in others' lives to their own. People can compare the world to themselves in terms of how they themselves can improve around their surroundings.
Another way to look at this is to think of appreciations that come through comparison. Like in this image, there is one artful chess piece that stands out in a dull background including an abandoned building in a city, which is viewed as a glamorous/high-class place to some... Comparison lets people appreciate smaller things in life because those smaller things stand out more.