There has been largely consistent randomized controlled trial (RCT) evidence in health care workers that wearing surgical masks and N95 respirators can reduce the risks of respiratory illnesses including severe acute respiratory syndrome (SARS) by 40–60%, after accounting for key confounders such as other protective equipment or hygiene measures.8,11 However, uncertainty remains as to whether surgical masks are inferior to N95 respirators in preventing infection. A recent meta-analysis shows that, compared with surgical mask use, use of N95 respirators is associated with a >50% reduced risk of overall clinical respiratory illness but has no apparent superiority in preventing viral infection,11 which is supported by a more recent large-scale RCT in an outpatient setting.8 Despite the potential superiority of N95 respirators over surgical masks, the evidence in health care workers defies a common claim that surgical masks are ineffective for prevention because some coronaviruses (e.g. SARS-CoV-2) may be airborne in specific scenarios (e.g. during aerosol generating procedures) and/or can infect people through the mucous membranes of the eyes.

Keep in mind,the covid virus is 100nm (wavelength of visible light is 400-750nm... If we were actually trying to filter out particles of that size it would be very challenging... but the virus is not terribly likely to be released from a carrier as a single free-floating particle. They will be released mixed into far larger droplets.

About a year before covid I had to really research filtration of small particles because I was concerned one of my projects was generating nano-particles of metal. HEPA filters are certified to "remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 300nm or 0.3µm."

You might assume that this means that they would not filter particles the size of the covid virus (~100nm), but that is not the case... they can be very effective, they just are not certified for particles less than 300nm. Smaller particles are very effectively removed by electrostatic attraction to the small fibers of the filter material.

But again, the particles you need to block are not so much individual virus particles, its larger droplets carrying 1000's or millions of viruses.

Social distancing is important too, but sometimes you have to be around others. Masks protect the wearer, and more importantly they greatly reduce the chances that an infected person can infect others.