It is — general findings are that the general use masks are helpful in reducing pathogen transmission through droplet dispersion by the person wearing it, but only if regularly replaced and coupled with constant hand washing (as people still constantly touch the masks as they do their faces).
There is very little to no evidence that they protect against violent aerosol dispersion (sneezing/coughing) of pathogens, either for the wearer or those around them, and can actually increase transmission if not used properly.
They are primarily used in medicine (consultation, surgery, etc.) to reduce transmission through (non-aerosol) fluid exchange and to make patients feel better about the cleanliness of the treatment space (which, believe it or not, is actually somewhat impactful on recovery rates). There are specialised masks that are much more effective, but those are not widely available and tend to be very expensive.
Coughing/sneezing in to your elbow away from other people, constant proper hand washing, and quarantining yourself when you think you may be sick are still the best methods of hindering transmission, short of wearing a hazmat/bio hazard suit and going through constant decon procedures.