Because they are protected by a superpower that allows them to continue their way of life.
> I'd prefer society to be like that at large.
So you'd be fine with giving up a good chunk of your life expectancy? Because that's what the simple societies of the past involved.
You'd be fine with giving up modern medicine, sanitation, sewage disposal? You'd be fine with having to work all day just to produce a bare subsistence amount of food, so that your body wears out much faster than in a modern society? You'd be fine with no Internet, books being rare and expensive (no printing presses), travel beyond your local village being a huge undertaking? You'd be fine with no modern hospitals, no 911 to call, no ambulance to come get you if you're injured or have a heart attack or stroke? I could go on and on.
People who yearn for "the simple life" only do so because they have never actually experienced it and have no idea what it actually entails.
The "Amish community" is a general group with a specific heritage that follows certain principles. They live in many different states.
Actual Amish people do live in a communal way, share resources, help each other, have common church practice, etc, which makes their local communities (not "the Amish community" in general) communes.
The Amish have been going strong for centuries, so there's that.
But I didn't say I want a niche commune anyway, I'd prefer society to be like that at large.