I have friend who works for 911. And I agree that the people who do the job don’t consider it a last resort. But of the people who “apply” for the job, I suspect many do simply because of the reputation for impacting a person’s mental health. But the rest of what you said gives me another potential cause. Drug testing. It possible some didn’t read the application in full or misunderstood some of the ongoing testing that happens as part of the job. The first interview probably enlightened some of them on the subject. That may cause them second thoughts after scheduling the shadow. I would expect it to be even more the case if the scheduling of the shadow happens the same day as the first round of interviews. But many people will see scheduling the shadow as nothing to lose, and delay deciding if they really want to go foreward until the last minute.