Otherwise, they lie in bed at night wondering why they got the shot in the first place.
There is a creepy factor to it.
It does seem “mandatory”, like someone took them aside and handed them a script. Or, as you indicate, perhaps they feel feel like schmucks, wondering why they made a horrible choice — and then go into denial and feel compelled to tell everyone that it wasn’t a horrible choice: it’s the best choice they’ve ever made.