I may be mistaken about this but I'm fairly sure that this is a decision that would be reached because of political pressure more than anything. The "they can't do any harm" attitude is oversimplistic: anything that has only a limited effect if used properly, but may actually worsen the damage if used improperly, ought to be carefully considered. For example, wearing face masks may encourage people to be more relaxed about social distancing, which would be a clear mistake.
Only proper masks can be regarded as truly effective -- and even then they aren't perfect, of course -- and they are best left available for the frontline healthcare workers who need them most.