I am of the opinion that if the typical person is hit by lightening and we add up the liabilities and assets that we will find most people are worth less than zero.
Although I sadly agree with you, I also have to consider it largely self-inflicted. Once you enter the workforce and pay off your student loans, you should only go UP from there (with the first year of a new car as the exception, though if you can't afford that slight dip between value and equity, you shouldn't buy new cars). We as a culture simply have a really bad habit of living far beyond our means. Make no mistakes, creditors fully exploit that habit, and no doubt someone will reply that they fall into the 1.4% with some insanely expensive medical condition, but in most cases it still comes down to choosing to spend more than we make.
Outstanding mortgages, car loans and other loans are only part of the issue.
A pretty big part - Short of end-of-life care, most of us will have no bigger outstanding debts than mortgages, cars, and student loans.
the cost of dying and the costs of burials as well as the cost of settling estates
Not material - Although it varies by state, you can get your body disposed of for under $100 (I've often seen $300 cited as the floor for a "cardboard box of ashes", though other cheaper options exist). And for an "estate" with negative net worth, your loved ones can always refuse to have anything to do with it and let the state eat the cost (though most people choose to "do the right thing" for dear-old-$30k-in-debt-dad). And as for the cost of dying, I can guarantee you that my end-of-life care will never push my net worth lower than the price of one last bullet. Again, we choose to drag out that last pathetic six months, at phenomenal expense both financial and emotional. No thanks!
The support of your kids, their education, your widow's needs all are considerations.
Can't afford kids? Don't have any. I realize that counts as all-but-heresy, but seriously, kids cost a lot; if you can't afford those three teens you mention, consider having just one, or even zero. As for your widow, if she can't support herself, you chose poorly in marrying someone incapable of surviving in the modern world in your absence. I want my partner fully capable of getting along without me in the event of my sudden death; I would consider it nothing short of cruel on my part to have her financially dependent on me, and that doesn't mean buying some scam of an insurance policy, it means she can very much support herself on her own income and retirement planning (though admittedly, if I die before we pay off the house, she'd likely need to find a new partner with which to split the household expenses).
Don't get me wrong, I realize we have some wiggle room here, and don't mean this quite as monstrously as it probably sounds. But bluntly, it all comes down to choosing not to live within our means, and you describe some of the biggest examples of that. Choose better