Firstly, the simple fact is thermometers are cumbersome to use. Even hand-held thermal devices present an inefficient way of screening people. The process is one-by-one, meaning it takes longer and requires several staff to conduct these checks. All of that takes time and money.
Thermometers also don’t have the accuracy of thermal imaging technology, and in a time of heightened consideration about contact with others, thermometers also require staff to get up close and personal with the people being screened.