Why are there no direct studies on if these things actually work?

Recent studies are always studying some secondary effect, and inferring that masks may help. For example, the famous study on visualizing droplets with lasers, that concluses the masks may help stop coronavirus by blocking droplets. But that isn't a direct study on whether or not they actually work.

Clinical studies in the past on masks have always found they do not protect against viruses. They were recommended only to help healthcare providers from getting splattered in their mouth, or to not drool in a patients open wound.