Our genes are heavily evolved to live in calorie scarce environments. In those environments, high calorie foods are amazing. Our biology is built to find them incredibly rewarding.

Science and capitalism have created incredibly delicious foods that are nutritionally lacking, hyper optimized for (against?) our now mis-aligned reward system. In the west, calories are not scarce and the most delcious foods are far from the most nutritious. It will take a long time for our genes to catchup.

Mass producing delicious, cheap, but low nutrition food is profitable. Companies have gotten very good at it. That's the real big change.