Interventions work differently for different diseases. Influenza is significantly hampered by social distancing, surgical masks, and elbow coughs.

Covid 19 is a different virus and the interventions of a flu pandemic are not going to yield the same results.

Infection is a binary status. You are either infected or not. There is no such thing as half infected or slightly infected. The probability of infection goes up when the air is more and more saturated with airborne virus... When air in a poorly ventilated space is fully saturated with virus, it simply does not matter if you wear a surgical mask or not as these interventions are doing nothing of significance for you in that situation.