I have never had any of the problems you mention about cards, except occasionally having to search a moment in my handbag. But a wristband, made of what? Something sweaty and unpleasant? The medallion, what ever that may be, possibly catching in one’s clothes, or disappearing under several layers on a cold day, or getting entangled with my watch. I do wear a watch, which has some of the above problems, but never wear bracelets for the reasons above.
Smart phones won’t do, because a number of passengers don’t have them.
Perhaps we should go back to actual keys.