[sleepychu]

Assuming you mean COVID-19 it's because the virus is not airborne, confusing since it can infect you "through the air".

The virus lives in droplets of bodily fluid, when you're closer than 2m just speaking with someone else is enough to exchange droplets and spread infection.

It's of course possible that someone walking by your window will cough out some droplets and they might be carried through in the air and infect you but the aim of the social distancing precautions is to reduce the infection rate and spread, not to prevent anyone from ever getting the virus.