As for why one thing is better than another, it's a sense that I get when I walk away from a good book. A deeply satisfying feeling. Sugar tastes good, I could eat candy all day, but try to explain to someone who only eats candy the satisfaction you get from a good, home cooked, southern meal. Biscuits and sausage gravy, fried chicken, grits, collared greens. If someone offers me a Reese's peanut butter cup, I'll probably take it some of the time - and I definitely don't want to eat a full meal all the time.
But the vast majority of people have ONLY been eating plain sugar - they don't even realize there is a whole world of different ingredients and foods out there. Most people exposed to other foods don't go back to only eating sugar - and that's because real food is better. It's not something you can deduct with logic, and it will never be done in an academic/research setting because it's taboo in academia to make value judgements about culture.