No one forces you to measure flow, level or pressure in your process (unless maybe your process uses HPP for sterilization).
Sure, these measurements are important—along with a host of other process variables you could instrument. But temperature is that one measurement that’s dictated by governmental regulations to prove that you have a kill step in your process. Beyond that, there are rules for keeping fresh food under a certain temperature to keep it safe both in transit and storage, and—just as important—maintain its quality so you don’t have to throw it out prematurely.