There was, as far as I can tell, little evidence at the time that the general public wearing them was effective at stopping transmission, and there were worries

There was, as far as I can tell, little evidence at the time that the general public wearing them was effective at stopping transmission, and there were worries that poorly fitted masks and poor mask discipline could actually make things worse. There are logical ways in which it can be true that they are useful for health workers but not for the public. We know they aren't correct now, of course, as there is now evidence.