I know that security agencies sometimes ask for passwords or try to convince you to hook your phone up to their device. If you travel often, you might want to have a secondary phone that doesn't have any sensitive information on it. You can (and should) also fully power off your phone when going through security because that'd make it insanely inconvenient for them to waste their time trying to get into your phone since the encryption only fully protects the device when it's powered off.