Or maybe they just prefer 'em because they're sweet and tasty.
C'mon folks, don't you remember being a kid? Sweet food tasted awesome, whether you'd seen an advertisement for it or not. Human beings, and especially children, are hard-wired to find sweets delicious and carrots merely tolerable. This made perfect sense to our prehistorical ancestors, since if they ever did manage to get access to something sweet it would be an excellent source of much-needed calories which should be prioritised.
See http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2235907/?tool=pm...