Parents. Pure and simple. Sit the kid in front of the computer or TV to babysit. Mom would rather go clubbing with her gal friends or dad go golfing all day to get away from the rug rats. No guidance for the kids. Mom and dad OD in the car, Mom and dad deny them food, chain them up, use drugs in the house, get drunk in the house, pass out and little Jimmy wanders out the house in just a diaper in the middle of winter. Most parents today are stupid pieces of shit. They love making them but they don't like raising them.
And BTW, my sister in law let her kid play video games every day of his life. He's now about 400 pounds or more due to inactivity and likely won't live past his 30th birthday. Thanks mom.