Largely because it's aggressively sold them to them by people who spare no expense and endlessly scheme to improve their ability to manipulate and coerce.
As the smarmy corporate cynic who's featured in this clip points out, it doesn't matter if the product is good or bad, or if the methods used to sell it are ethical or unethical, their only goal is to sell it.
This is the attitude of the entire food industry, including the so-called "health food" industry. And kids aren't the only targets.
A simple rule of thumb for you and your kids
If it comes in a can, a bag, a bottle or a box, it's suspect. If it requires a label listing its ingredients and it comes from anywhere other than the produce section or bulk bin, there's already a problem with it.
This is simple. The closer the food you eat is to its original form when you get it, the healthier it will be for you.
It takes hundreds of millions of dollars worth of manipulative advertising each year to convince you and your loved ones otherwise.