There is also a lot of stress we don't have to deal with - at least here in the west, like keeping food stocked for winter, worrying about bears and wolves, worrying about various crippling or deadly diseases that used to be commonplace etc etc.
Those are some things we don't have to deal with, but what's the connection with "stress"? Did people actively worry about getting leprosy or polio? Was that really a cause of "stress"? Perhaps it was; I don't know. For me, driving in bad traffic, when I'm late for an appointment, can be stressful, but thinking that I might get Alzheimer's, so perhaps I should sort out wills and power of attorney... not so much. And if we didn't have today's complex legal system, they'd be nothing to worry about at all, because what could I possibly do about it, except perhaps attend mass and say my prayers?
Opt out is not a real option. The world is not set up for that anymore. What are you going to do -- go squat illegally somewhere until someone chases you away? Eat pigeons? It's not as easy as you make it sound to escape the framework of our society. I'd love to be proven wrong.