[isolli]

Surgeons don't wear masks to prevent the spread of airborne diseases. They wear them to prevent spittle going into an open wound and to protect themselves from blood splatter.

If they wore masks to prevent airborne diseases, they would wear them when meeting patients, not just during the operation.

[sobani]

The difference is during a regular meeting, the skin is uncut. The skin is a major protection against diseases and the body has a bunch of mechanisms at its regular openings (nose, ears, etc) to protect you.

When you cut through someones skin, you bypass one of the major first lines of defense. Therefor surgeons reduce the risks, for a similar reason why clean their tools before use.