Hmmm...depends on a lot of things. For example, your family background. But I assume that most NBers -including myself - are not born millionaires.
Anyway I'm not from the US so let me add quickly that here highschool is 4 yrs, preceeded by 8 yrs of elementary school, and -if you are admitted- followed by university, which is usually divided into BA/BSc and MA/MSc (but my faculty, law, f.e is undivided, which I used to think is a good thing but lots of shit happened and having run out of the time limit for state scholarship, I'm still without any paper, after 6 yrs, and whatever I earn, goes for tution fee so I've concluded that this system was/is a trap -probably designed to make students resort to take student loans, economically enslaving you for half of your life-, and now I wish I had been wiser and chosen a BA/BSc education first after which, having some kind of a certificate in my hands, I could have decided whether I want to go for masters, or an undivided major like law [in the meantime, as so many years have passed, I could have started and most probably finished a secondary major in the BA/BSc system like many others do, but alas that would cost even more tution fee so, as my parents are not that generous and I can't earn that much with student jobs, well, this option was/is not really feasible]. )
So, in a situation like mine, I have no choice but to keep going and one day get my diploma into which I invested so many regretful and hardworking years... And again, the funny thing is, my prospective law degree with the title 'dr' is worth the same as a BA/BSc degree, at least in state/public/government-related jobs, so yeah, I must say that if you are not exactly sure about what you are interested in- as I wasn't either when I was 18-, and if your financial/family background is not solid enough, then be careful.
Now everything I said above matters only if you wanna pursue higher education after highschool. Of course if you want to go to uni, you need a highschool degree. In that sense, yes it's important.
At this point I have to specify that basically we have two types of highschool: secondary grammar school (where you can major in typical subjects like history, languages, maths, physics...etc, and usually people choose to go to uni with a secondary grammar school degree), and then there is technical highschool that basically gives you a trade (like, a cook or a welder or a mason...etc). And there is also an option that after highschool you can enroll in courses (that take 1-2 yrs) that give you a trade (f.e assistant, secretary, or even street-policeman XD )
I don't look down upon physical work, actually I kinda envy those handymen that can fix anything around the house...it's just I was more like the brainy type so I thought I'm rather fit for a white collar career...But honestly, I think that's overrated. I know many people having graduated from the faculty of arts with a history or a literature degree working at McDonalds or migrated to some rich Western-European country working for Tesco...etc. The only degrees nowadays that the market needs are medic, engineering, IT, science related ones. But well, I can't help it, I'm stupid when it comes to IT so it was never really an option for me >.>
But again, you are in the US, so I guess you can make a fine living with a single trade, without a higschool degree...at least, if you're not too picky...But I don't know what is the current situation exactly like.
Now, I know someone who is younger than me, has a highschool degree but it's not like he needed it, yet the guy started his enterprise (some online webshop selling designer clothes), and he's pretty rich now. But I guess you need a talent for that too, I doubt I could ever start a company of my own and make it profitable in the long run...
Now I also know people who are self-employed musicians but they barely get invitations so I guess not all sectors of entrepreneurship are paying off...
Btw...at the end I must mention the most important thing...at uni I literally had to use less than 10% of the stuff I learned at highschool (keep in mind that we're talking about law here, so maths, other science-related subjects, are all irrelevant here, and sadly they don't put any emphasis on foreign languages [but beware, employers will, later].)
Anyway, if my memory serves, you are a nurse, which is a really good profession (I dunno how in the US you can get that education, here it's a trade that doesn't require uni degree, but a higschool [the technical one] degree ).
I dunno if the above helped, altogether it's always useful to have some kind of a degree (whether a certificate that you've mastered a trade, or a uni diploma), but if someone is witty and hardworking enough, the person can make his own fortune by starting an enterprise. Or else he will be an economic slave working 3/4 shifts in a factory for minimum wage (which is still much better in the US than here). But really, it all depends on what your/his/someone's goal(s) are/is. If someone just wants to make an average living and doesn't mind taking the most shitty jobs, I guess then there is no need for any form of higschool degree, but I don't see why someone would choose that unless he has simply no talents, or simply his family background was so shattered that he had to leave highschool. Apart from these, I don't mean to stereotype others, but dropouts are either lazy or crazy (either case, be careful, but of course you know the guy you mentioned, so maybe he is decent and intelligent nonetheless).
Just my 2 cents.