Your comment sounds good for overland rail, bus, event tickets, airlines etc and indeed QR is common. But for subway/metro, during rush hour throughput it is i

Your comment sounds good for overland rail, bus, event tickets, airlines etc and indeed QR is common. But for subway/metro, during rush hour throughput it is important to able to tap an RFID almost instantly. QR is too slow and error-prone for subway/metro. The world (including Montreal - these tickets are going away) has converged on credit card / phone / top-up charge card for that reason.