But we don’t live directly on top of the ground; we live 5 or 6 feet above the ground, and thus air temperature is much more important to understanding heat impacts to human health and well-being.
Here’s an article talking about the types of temperature measurements. If LST is high, odds are air temperature will be high to, and air temp is much more relevant to our life as a human, whether we’re going to die, and easy to compare to how hot it is locally.