> Why do we need studies for things we've known for centuries?
Because folk wisdom is not science. For example, many people enjoy a cozy fireplace, but increases chances of heart/lung disease a significant amount due to small (PM10) particles: https://www.epa.gov/pm-pollution/how-smoke-fires-can-affect-... https://www.lung.org/clean-air/at-home/indoor-air-pollutants...