I've been to many concerts in the past couple of years, and all the time people are always on their phones recording or taking photos for social media (I'm guilty of this too), my guess is, since Swift's main audience is teen girls most of them probably spent a majority of the concert on their phones. Completely unplugged from reality and the performance they were there to see. So their brain probably just blocked it out as more time spent scrolling and posting on Instagram, Tik tok, and Snapchat.