Why do we enjoy anything, why are we attracted to certain foods/activities and indifferent to others? Our body manufactures opiates and we get a little pleasurable rush. That causes us to do it again and it strengthens the neural circuitry in the brain to seek out that behavior to get the rush again. This is actually a good thing if we lived in the time period our physiology was adapted for. If you were blaise about eating you might not be motivated enough to seek out food.

Certain foods we eat are also broken down into peptides that can bind to opiate receptors and they are small enough to cross the blood brain barrier.

Now you can decide for yourself where to draw the line between addiction and just liking something, but this isn't entirely about conscious decisions. We have an elaborate hormonal/electrical system that plays into these things. While I might consciously realize that I should stop eating ice cream after I've had a single serving, there's a lot of unconscious factors that are not entirely under my control that make it very, very hard to stop going back for the next serving.

It's like that old saying, "I can quit anytime I want... I just don't want to."

Unfortunately the more you reinforce a behavior the harder it is to change.