"Introverts Unite!
Separately, in your own homes.

"
No, seriously though?
I think it's a combination of things.
For one thing, technological advancements over time have made it to where it's easier to be alone than it used to be decades, centuries, and millennia's ago.
Too much social isolation was dangerous in histories past before the advancements of modern medicine and science. Because our bodies are 60% water, the most probable causes of death in ancient times was disease and viruses, followed closely by famine, and then most likely murder. These aren't really problems we have to worry about as much so anymore, save for murder as humans are still quite excessively violent.
If you get sick and have an infection or a virus you go to the doctor and get vaccinated or get antibiotics and in extreme cases emergency surgery, but basically most things are treatable these days, lest you're particularly lacking in intelligence and decide that ether is a drug worth trying and ignore the fact that it contains a percentage of sulfur, in which case I mean it probably won't kill you BUT eventually it will because that can't be good or your internal organs.
The thing about solitude when you're introverted in particular is that it can become addictive in its own, and often without us even really realizing it. Solitude is helpful because we need to recharge our energy as socializing is exhausting to us, but equally so too much solitude is dangerous to our mental health in a similar way that the occasional alcoholic beverage for special occasions is fine and mostly harmless, but day drinking is really unhealthy (and I can say that, as I'm a recovered alcoholic).
And if you're a creative introvert, well then you really can keep it up for forever by just perpetually creating new ways to keep your mind going. The downside of this is that in instances in which you actually need assistance from other people it either isn't there at all, or attempting to get assistance will just fall through due to your natural lack of or underdeveloped social skills.
For example, while I'm told by people that I'm well written and well spoken and seem intelligent to them, when I was in my mid and late 20s I had lots of trouble with cars that I had. They'd break down, I'd have to get parts, I worked far away from where I lived at the time (upward of over 10 or 15 miles away) and because I didn't really have the knowledge, tools or skills to do something like change a water pump because I was never taught how to, repairs and replacements costed me a lot of money, and walking to work every day for about 3 weeks not only sucked but also I was too tired to even begin to learn how to assess my car myself. Even now that I'm in better health and am more used to being in that kind of a situation, 10 or 15 miles is still 10 or 15 miles, and an 8 hour shift of standing is still an 8 hour shift of standing. The situation is an impractical situation. I did occasionally have coworkers that would give me a ride back, but that's mainly because they understood the full spectrum of it as they happened to be going that direction to get to their homes too. During this time period I spent most of my time alone when I wasn't at work, it was actually a very hard time for me, and this is how I discovered that too much loneliness can be dangerous to your mental health.
The Prefrontal Cortex of the brain is also where Rumination occurs, which is what happens when your mind Idles too long and you start thinking about negative things rather cyclically in what is called the Default Mode. There are a couple of different ways that this can be assessed: In times past, that would be why housewives used to be given lobotomies for depression which, because it's a lobotomy, of course it would screw up their cognitive functionalities a bit and that's how you get ridiculous home remedies like putting cold meat on your face to reduce swelling (while it does help, it's no less a ridiculous notion). Usage of psychedelic drugs can stimulate neurotransmitter growth which actually helps fight against this as well, but the most common treatment is SSRI's and therapy.
A generalized lack of compassion or empathy is a growing concern and problem in society, which also does not help. This occurs in part because of the uncanny and unfortunate part of the human mind to rely on other humans as utilities. Because we're thinking of other humans as utilities or tools, we cannot assess them as the cognitive and sentient people that they actually are. This is the problem with the idea of social constructionism and the part of the logical deductive reasoning mind, is that the part of the mind that sees others as a tool or a utility and/or resource is a different part of the mind than that part of the mind that actually understands people as the cognitive and sentient beings that they actually are. That's the problem. It's a bit like a car stereo system: Can it play tapes and/or CDs? Yes, it can. But is that what it's best used as? No, it's mostly best used as a radio (unless your antenna is broken).
The other part of the problem is that combating the external assumption of yourself as a utility, tool or resource to other people is legitimately challenging BECAUSE they're not looking at you from the proper perspective of you as a cognitive and sentient being. So, you've gotta shake them up a little. That's challenging and difficult to do because with some people they just won't understand why it happened or why it is happening. A bit like interlocking a couple of wrenches on a tensioner to loosen up a serpentine belt system: Too much tension and you'll accidentally break the wrench. Some people will instantly know why the wrench broke, other people won't get it and will only get angry and upset because the wrench broke. It's a polarizing experience to give kickback in your own defense, is why people react differently to it. And the problem is: That's not your problem, and there's kind of no way to avoid that, so it's just something you kind of have to get used to doing which can cause a lot of tension and/or screwing up of your relationships with other people.
I think that if people actually understood that it's a problem with comprehension and understanding more than it is a problem of self-interest that things would probably go smoother in such turbulence. If the angry person who broke the wrench by accident actually understood that the reason why the wrench broke was their own fault be it accidental or otherwise, a lesson is learned on what not to do again. But they don't understand that. What they understand is that they have a problem that they now cannot assess and they do not know why. And therein lies the miscommunication. They're supposed to care, it's supposed to matter, but because they don't care and it doesn't matter to them that is why they do not understand or get it.
*looks back at this post*
Apparently I just improvise writing biblical script when I post.