Millennials are the most underinsured generation alive today—which makes a certain amount of sense. They have relatively few assets or dependents to protect. Still, the gaps in coverage are striking and offer further evidence that this generation has been unusually slow to launch. Roughly one in four adults aged 18 to 29 do not have health insurance, twice the rate of all other adults, according to a survey from InsuranceQuotes.com, a financial website. (Other surveys have found lower uninsured rates, but this age group is still the most likely to go without.) Millennials are also far less likely to have auto, life, homeowners, renters, and disability coverage. Young adults have always been slow to buy insurance. They often feel invincible when it comes to potential health or financial setbacks. But something additional appears to be at work here. This generation has famously overprotective parents who awarded them trophies just for showing up. Millennials may view moving back home or calling Mom and Dad for a bailout as their personal no-cost, all-purpose insurance plan. Millions of young adults routinely boomerang home after college or get other family financial support. The trend is so broad that psychologists have given this new life phase a name: emerging adulthood, a period that lasts to age 28 or 30. MONEY explores this trend, and its costs, in the September issue reaching homes this week. Remarkably, the parents of boomerang kids don’t seem to mind providing the extended support. A quarter of parents supporting an adult child say they have taken on additional debt; 13% have delayed a life event, such as taking a dream vacation; and 7% have delayed retirement, the National Endowment for Financial Education found. Yet 80% of such parents in a Bank of America Merrill Lynch survey say helping is “the right thing to do,” and 60% are willing to work longer, 40% to go back to work, and 36% to live with less if that’s what it takes to help their adult kids. “Millennials have had very supportive parents throughout their life,” says Laura Adams, senior insurance analyst at InsuranceQuotes.com. “When you don’t have a fear of the unknown, a fear of life’s what-ifs, you are not likely to think about insurance.” Yet young people overlook certain types of insurance at their peril—even though these policies may be relatively inexpensive. Most striking is how many skip health insurance, even though the Affordable Care Act mandates coverage and allows children up to age 26 to remain on a parent’s plan. Millions more young people now have health coverage as a result, recent studies have found, and their uninsured rate has dropped. But, still, as many as one in four still go without. This may be classic pushback against a law young adults see as unfair. They understand that their insurance premiums subsidize the health benefits of older Americans who are far more likely to need care. Yet if Mom and Dad won’t pick up the bill, a visit to the ER can cost $1,000 or more for even a simple ailment. Things get much more expensive for broken bones and other treatments that even the young may need. Among other findings: 64% of millennials have auto insurance, compared to 84% of older generations. Many millennials may have decided to skip car ownership. But if you rent a car or borrow one from your roommate, you have liability. It probably pays to have your own policy, which might cost $30 a month. 10% of millennials have homeowners insurance, compared to more than half of those aged 30 to 49 and 75% of those 65 and older. Fewer millennials own a house, for sure. But this generation isn’t buying renters insurance either: only 12% have it. Renters insurance is cheap: $10 to $15 a month, and it comes in handy not only when someone steals your bike from the storage area but also if Fido bites a neighbor. 13% of millennials have disability insurance, compared with 37% of those 30 to 49. This kind of coverage costs around $30 a month and may seem unnecessary. Yet one in three working adults will miss at least three months of work at least once in their life due to illness, Adams says, adding, “Anyone can throw out their back.” 36% of millennials have life insurance, compared with 60% of those 30 to 49. Again, this coverage is relatively cheap: around $20 a month for $500,000 of term life. If you have no dependents you might skip it. But if you have debt that Mom and Dad co-signed, you should have enough coverage to retire the debt. It’s only fair, given your parents’ years of extended financial support.