Then they can just skip insurance. Most people don't need it, especially if they already have a lot of money (which is what FIRE means)

That plan works until it suddenly doesn't. When it doesn't it's catastrophic for your finances and your health.

If you have an extra couple million dollars above and beyond your regular retirement fund you could self-insure your medical costs. But then you could just buy the health insurance.

Obviously said by someone who is young and never had or knew anyone that had an expensive medical procedure like a friend who is 45 who I have known since 2003 and is a cancer survivor and now has to have open heart surgery