I wonder what the age breakdown is. I could see a lot more younger people never having needed to get credit yet. If you still live with your parents and go to college or whatever you don't really need credit.
After that though you can't even really rent an apartment without a credit check so I'm not sure what you would do (I guess if you have a partner that handles it for you).
It is mostly the unbanked who have no credit. College track kids often get their first credit in the form of student loans or low limit student credit cards.
There are plenty of places that rent without credit checks. Where do you think all the people with no credit (or no SSN!) live? It might not be on the nice side of the tracks, though.
After that though you can't even really rent an apartment without a credit check so I'm not sure what you would do (I guess if you have a partner that handles it for you).