Another different example; same red light, same you running it, only one guy in the other car... which is now a brand-new $80,000 BMW 6-series. Just to spice things up, he had a $3000 laptop in his briefcase on what used to be the passenger seat, that's now a crumpled hunk of metal and silicon. He's fine, thank God, but seriously cheesed off that his laptop and his midlife crisis are total losses. Your 50/100/50 plan? Leaves you on the hook for $33k in property damages. A 100/300/100 plan would have covered it in full (albeit probably putting you on public transit or a van pool for the next 3 years; a driver who totals a car worth more than 50 large is automatically put in the highest-risk pool of covered drivers).
So, to answer the question, look around. See the other cars around you on the road on your next commute. What is the average blue book value of those cars? How many people, on average, are in each one? You pretty much need insurance sufficient to ensure you can walk away from an accident not owing a penny for any level of damages you may incur that don't result in permanent disability or death.
Insurance for those eventsdeath and disability is not the kind of thing the average person can even afford; the average judgement for wrongful death is $2.9 million according to another number I pulled off Google. To be fair, that figure probably has a lot of medical malpractice - translated: deep pockets - figured into it, but wrongful death judgments in general are some of the most expensive you'll ever see. Consider future earnings potential alone; if you make the median $55,000, and you're 30 and plan to retire at 65, you would expect to make $1.925 million in that time. If someone accidentally killed you tomorrow, that's the least your family could expect to get in a judgement.