BDL (Bradley - Hartford/Springfield) used to also ask for BPs out, and when I (kindly) asked a TS"O" why this was different from other airports, he said it was their manager's discretion. Being as I always use a mobile BP anyway, I just got a snarky look when asked where mine was and me saying it's on my phone. They've since backed down from the policy in the last couple months and don't check BPs twice, when I've been there at least.

Unrelated, BDL also has ONE mobile BP scanner, and the line isn't even "mobile-only" dedicated (they have 5-6 lines total). Why should I be punished for using technology and having a bunch of people with paper BPs making the line longer? The inefficiency is baffling.