Two things to consider.

1. A clear test means, assuming it is done properly, that the tested individual was free of the virus at the point in time the test was carried out. It does not mean that they are clear for ever more as seems to be a general belief. In fact you could become infected immediately after testing or at any point thereafter.

2. To catch the virus you have to somehow come into contact with it. Where is one of the most likely places for someone who believes they may have the virus likely to be found? The local testing station would be a logical place for them to go.

I would agree that testing station staff and their procedures are good but humans being humans are never perfect so point 2 is still valid.