re: Why is keeping children on parent's plan till 26 so popular?

A) Because most parents probably don't care to pay the extra premiums (they typically aren't that high). B) The extra money is pretty good for insurance companies because they collect premium on a group of people who are highly unlikely to have claims that are higher than the collected premium. C) Younger people get to have coverage during the years when they are trying to figure their shite out. It's the rare situation where it's a win for pretty much everyone involved.