Hate to be that bastard but I just realized you can't hear shit on a helicopter without headphones.
Maureen takes her headphones off to yell at Jasper in the beginning of the book so screw it, we can say they are wearing ear piece or some shit if we want to get hyper technical.
Oh don't worry about being that guy xD The reason why they don't have headphones is one part forgetfulness, one part laziness, and another part 'I have gone this far without drawing it aghagahggh consistency....? Even if it's wrong....? Something something.'
At one point I literally woke myself up out of a deep sleep realizing they didn't have them on and then I was like 'maybe I will edit it when the book comesoutsssszzzzzzz.....'
Its a magical post apocalyptic helicopter.