One study that I know of that was done in the United States did temperature checks and symptom screens of everyone entering from the airport. Its estimate of effectiveness was 83,000 temperature checks and symptom checks to identify one individual that was positive.
Yes, they will pick up people, but you have to consider what the risks are. To me, also, having a lot of people standing in line waiting to get a symptom screen and a temperature check from an infection control perspective is like, “Oh, God, what is going on here,” right?