Why are we seeing so many dramatic media headlines talking about 70%, 75%, or 80% reductions in COVID-19 spread if we wear masks at the same time that leading scientific organizations are actually lukewarm on whether they help at all?

A couple examples below:

The most viral study today is one showing a 75% reduction in spread of COVID-19. What did the paper actually do? They had two cages of hamsters, one sick, one healthy, then put masks fabric between the cages and saw a 75% reduction in spread between the cages.

The most viral study in the previous few days is this one, claiming an 80% reduction in spread of COVID-19 with masks. What did this paper actually do? They started from an assumption that masks work (!!!), quantified their assumption, and then just showed how much that matters.

While we'll see more studies like the latter one, the hamster one is more symptomatic of the most common type of article we're seeing. They put mask fabric somewhere and show that viruses, liquids, or some other simulant gets through less often when sprayed/coughed/wafted.

But this is actually pedantic and obvious, and the only question is how to quantify it.

The tricky part is that in the real world, masks are worn for many hours or even days. What ends up happening is that the outside of masks becomes coated in viruses & becomes its own vector.

And this is even presuming that masks are worn correctly. To wear them correctly you must NEVER touch them without first washing your hands, and you must wash the mask after every use. You also must not reduce social distancing at all. What percentage of people actually do this?

This is why if you look in actual scientific journals you see much less dramatic and moralistic headlines. Basically, scientists throw their hands up and say "Meh, might work, hard to tell", such as this one: https://www.livescience.com/are-face-masks-effective-reducing-coronavirus-spread.html

If we wanted to focus society on an activity which more unambiguously reduces the spread of COVID-19, a much better option would be handwashing. This is easy, painless, most people don't do it enough, and there are no real downsides to excess handwashing.

Of course, it was probably inevitable that masks were going to end up the primary Culture War front, because they're so visible. Either you get to show off how selfless/"pro-science" you are, or you get to live out a childish fantasy of "resisting" tyrannical government.