It's not clear that it was EVER effective in any decision-making. In the early days, there were so many false-positives (WA State) that I pretty much know nobody who cared. And so many false negatives that you had to test ANYWAY if you had any symptoms or any personally-known exposure.
The problem is the app gives NO indication of duration or intensity of exposure, nor of the timing of the person you're exposed to.
Almost pure theater - caring about the appearance of safety, not actual safety. Good Riddance.