Because the food that someone had growing up or while away at college, either tasted so bad, or was such poor quality, that they had to hide the taste with something else in order to make it palatable and they couldn't afford to not eat it.
i.e. ranch dressing or ketchup on burnt or over-cooked anything.
They also, in turn, have gotten conditioned to eating this way so they still have to do this to almost all food they consume.
Person 2: You didn't even try it first, you might like its natural taste.
Person 1: I like the natural taste of ranch dressing. I drown everything I eat in white trash ketchup!