If 70% of people get it, you have a baseline risk of 30% of getting it.
My assumption is that a sizeable fraction of people either:
* Already got it
* Don’t take hand washing seriously or do it wrong
* Are bad at avoiding touching their face
* Unnecessarily touch surfaces when out (i.e. door with hand, rather than sleeve/bag, whatever)
* Don’t practice distancing well
* Are in a job where they must interact with the public
If you do all of the above correctly, my guess is you can raise your odds of avoiding from 30% to 50-60%.
It’s not based on any math, but I don’t think there’s any definite math to base it on. I could be wrong in either direction.
Nonetheless I think it’s sufficient to argue that it is not inevitable that and individual will get it and everyone should not even bother to avoid it.