I really can't see a valid objection to carrying a plastic railcard (if needed) and a paper ticket, (be it CCST, PRT or printed e-ticket). A railcard weighs about 5gs as does a single A4 sheet of 80GSM paper. For those that don't want to take the risk on mobile technology malfunctioning, or their memopry malfunctioning by not ensuring that their mobile device's battery has a sufficient charge, but expect to be able to continue withou penalty when their choice and use of a device prevents them being able to prove that they have authority to travel, the extra 10g is hardly going to weigh them down. Of course those paper/plastic items can be lost/stolen, but so can a mobile, a charging cable, a power bank etc., - the responsibility expected af an aadult when travelling by public transport is hardly a challenge.