I read researched this a few days ago.
You have to consider the taste, it tastes nicer because fructose has only 5 carbon in it's ring instead of 6 which leads to more pleasurable experience as it makes it fit better into the sweetness sensing in the mouth[1]
With Corn Syrup you get both glucose and fructose together whereas with sugar you just get sucrose. Another reason would be that more corn is grown in the US than sugar cane which makes it more efficient to produce corn syrup instead.