Don't ask me that question. Mae West is (was ) the one to nail the answer:

Anything in life that's any fun is either immoral, illegal or fattening.

But joke aside, our love for sweets, for example, has an evolutionary reason. Sweet taste signals sugar content. And sugar is our body's preferred fuel, for which we also have only limited storage capacity (unlike for fat). So it made sense to have our ancestors go for the fruits and honey. They, of course, had to do lot more to get them than to shuffle from the sofa to the fridge.

I'll touch on this subject in my next post.