Similarly, I am not required to go through the company in order to socialize with friends I made in that company. Indeed, I maintain friendships I made in companies I no longer work for.
Lastly, making friends through your job is how it always has been. Talk to your parents.
So in theory it’s not a limitation, but in practice it often is.
As far as I know, employers are free to terminate anyone having health issues that render them unable to perform their duties:
https://work.chron.com/termination-employment-due-ill-health...
FMLA (if employer has more than 50 employees) or a state disability law might protect employment for up to 12 weeks or so, but other than that, there is no reason a business has to keep a sick employee who cannot fulfill duties on payroll.
Switching insurance is a hassle. Maybe in some areas plans are more fungible, but where I live there are two main insurance companies with two highly disjoint networks. Switching jobs has a 50% chance of forcing us to also switch pediatricians, which is a huge hassle when the kids have finally become comfortable with our current one.
The people that get screwed are employees of employers that do not offer health insurance. They have to buy with post tax money.
My wife and I have chronic conditions- we frequently hit our annual max within the first three months of the year. If I don't switch to a new job before that fills up, I've wasted $15,000. For me, switching jobs is essentially a $15,000 fine.
So yeah, insurance being tied to a specific company is very much an incentive to stay with that company.
It's not like the before times where you'd need to visit a bunch of brokers and hope someone could find a plan you might qualify for, if you're lucky.
What you usually miss out on is non-emergency coverage outside your home area, whether that's limited to the state or county you live in depends, and sometimes it's pretty bad if you live in an area where it's common to cross county or state boundaries but the exchange plans don't allow that.