I'm fairly convinced that the messaging behind the "masks don't do anything" rhetoric is to prevent a shortage to people who need them. Yeah, everyone wearing masks would probably effectively slow the virus but if there's known supply chain issues and everyone stocking up would cause availability issues for doctors & nurses, then we have to take the lesser evil.
Media has to act as the Catholic Church did in ancient times. It has to make up some stories to control people's behavior.
Toilet paper is an example of this: you talk about a shortage, and people will buy more. They don't believe it's really necessary, but since they know other people are buying and the media is talking about it, even smart people understand demand will increase and stocks will fall, so they buy more.
Same with masks: if you tell people "they work, but don't buy them" it will have the exact opposite effect.
In China and other Eastern countries, this is dealt with by causing fear in people: "if I buy a lot of masks and the state finds out, I'll be in trouble".
We don't have that tool in free Western countries. So media manipulation becomes the only effective tool for behavior control.
Lying to people doesn't help public health or fix the problems of the federal government failing to act. The AARC told HHS to get their act together about the SNS on ventilators, but the govt didn't.