Why is there fructose in fruit? It's good for the fruit trees. Fructose is intensely sweet and inhibits your ability to feel satiated, so you'll eat more fruit (hence spreading more seeds). It's processed by the liver just like alcohol: the liver immediately converts it to glycogen (a stored form of carbohydrate). So, it makes you fat and hungry.
Note that prior to modern living this wouldn't have been so bad; fruit would NOT have been available year-round outside of the tropics, and it wasn't nearly as sweet before modern breeding programs (so I hear, anyway). Plus, back when food was hard to come by, storing a little fat once in a while wasn't a bad thing.
Conclusion? Fruit is better than junk food, but it is in the same category with regard to sugar content. Therefore, eat it sparingly.