While that's true often these types of weak observational studies are needed in order to fund more robust randomized and controlled studies which tend to be far

While that's true often these types of weak observational studies are needed in order to fund more robust randomized and controlled studies which tend to be far more expensive and need some even low-quality evidence to justify. In this case the evidence is particularly weak as even the paper notes almost every attempt at retrospective randomization or control makes the association basically disappear.