I have several friends with adult children (in their early 20s) who have jobs but no benefits. The parents are quite happy about that provision, even though they hate the rest of Obamacare. It's safer than having an uninsured kid and way cheaper than having a kid trying to buy private insurance (easily $7000 or more a year).
Whoever came up with the idea came up with a great marketing hook. Gotta say that much.
You must live in a pricey state. I bought a policy for my college-age son last month - it costs about $100 a month. It was cheaper, in fact, than carrying him on my own policy.