By King Snyder, Sartorius Corporation
Cereal companies extrude moisture on the production line. The dough has a very tight moisture specification as it goes through the extruder. Too little moisture and the cereal will break apart. Too much moisture and the dough will clog the extruder causing production to shut down.
There are many more examples for why companies test for moisture. For example, some government regulations require industries to provide moisture compliant data.