Why do we like sweet?

In nature, the sweeter the food, the greater the calories. Humans have adapted over millions of years to seek out food that tastes sweet, and not just for survival. Eating sweets can reduce levels of stress hormones, calm babies and relieve pain. Some experts suspect, however, that our desire for sweet things has been reinforced—and perhaps even intensified—by our environment. Susan Schiffman, a professor of medical psychology at Duke University Medical Center, has found that African Americans and Hispanics like their food significantly sweeter than the rest of the population—a result she suspects is from campaigns that market high-sugar grape and orange sodas to predominantly ethnic populations.

I hope this can help your understanding. :)

Sweet tastes good.