Kitchen and food-use thermometers are used for several purposes. One key purpose is food-safety. Another purpose is to gauge what state of physical transformation a food being cooked is at.
On the 30th of June in 1906, American President Theodore Roosevelt signed into law both The Pure Food and Drug Act and the Meat Inspection Act. The laws were the first step in the government assuming responsibility for assuring the safety of the American food supply.
The 7th of June is World Food Safety Day. Globally, foodborne diseases annually cause an estimated 600 million illnesses and 420,000 premature deaths. 30% of those deaths are children.