At risk means you have a higher chance than normal to be affected by a certain disease.

What the focus is when you say "at risk" is factors that will increase your chances of getting covid.

Since all of us living (hopefully) have lungs, there's a baseline level of risk and is pointless to point out. We only mention at risk when there's special factors other than "lungs" that increase our chance of getting a disease. By following this logic by simply being human you are at risk of diseases so the only way to not be at risk is to die