Whenever there’s some research paper on something obvious published in the “popular press” there are always commentators who wonder why. There’s a variety of reason why, but the first is by far the most important.
Just because something is known to be true doesn’t actually make it true. The point of proper research, experimentation, and evaluation is to test the truth of something and to verify that truth. Old wives tales may or may not be true (and some are), but until they are tested they remain just tales.
The second reason is to verify another researcher’s finding – a fact verified by one researcher (or research team) isn’t as fully verified as a fact verified by two or more.
And lastly, researchers have to research to learn their trade. Nobody would trust a plumber who hasn’t yet plumbed or an electrician who hasn’t yet fitted a plug, so why should researchers start with real problems?