I can give you some points
-Maybe they grew up with that food
-Maybe their family doesn't like it
-Maybe they have never eaten it or they hated the smell
-Maybe they tried it when they were younger and remember not liking it, or it making them sick
-Maybe they have allergies to a certain food
-Maybe it is just for health reasons
-Maybe they are on a diet and can only eat certain foods
-Maybe they eat that food because it is cheap or it is all that is available.
Hope this helps!! It's not much but I really hope you can do something with this information!!! :)