Only if those tests aren't more valuably deployed for some other purpose. Nothing in epidemic control is about perfection. You'll never be able to catch every single transmission. The goal is to reduce the average rate of transmission among the whole population, such that the average number of people infected by one new case (the "R0" number that keeps getting thrown around) goes below one. Once you do that, you win.
There can be difference in testing kits quality or perhaps just a false negative.