system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do unhealthy foods like junk foods taste delicious and addicting while healthy foods like vegetables dont?
gpt
For the vast vast majority of human evolution,  high-calorie energy rich foods were rare and hard to come by. Having a craving to eat as much fat as you could whenever it was available was a very good survival instinct because who knows when the next big meal is coming. And in the meantime maybe there's a flood or fire, or you get sick or hurt, or a drought happens. 

When any shit like that goes down, you're more likely to survive if you gorged on that dead animal you found and built up your energy stores.

Only very very recently (evolution wise) did high calorie foods become cheaply and *reliably* available, all the time. So what used to be a useful instinct isn't always suited now, but there hasn't been enough time to re-adapt yet. If humanity lasts another 50k+ years, all the obesity- and heart-related deaths from overeating will possibly push the balance and reduce our craving for junk food. But there's a million years of calories=life to overcome.