primarily to reduce the likelihood of infectious people infecting other people.

This is not complicated.

Every Single Avoided Infection Reduces The Pandemic.

Whataboutism is irrelevant.

The virus simply does not care about logic.

It only cares about math.

If I'm infectious and wear a mask and avoid infecting you, then you and everyone you would have infected do not get the disease (from me).

If I'm part of 5% of people who are actively trying to avoid spreading the infection, then it probably does not matter much and the virus spreads and spreads and spreads.

If I'm part of 90% of people who are actively trying to avoid spreading the infection, then it matters a great deal and the virus vanishes.

That is why we are doing this.