People should indeed carry such a charger for continuous, guaranteed uninterrupted power — but at the same time, no rational person who is OK with interruption would expect nineteen of them.
First, that's a very nasty disregard for others. Second, if we're applying "you should have thought of that" to rail facilities, we might as well be running flat wagons with "bring your own roof" instead of well-equipped intercity stock.
When I board a service and see what looks like seating, I don't think "maybe it will fold underneath me every now and then, I'd better just use this camping chair I brought with me". The same is true of a visually-standard BS1363 socket. You might just have a point that I'd disagree with if they were labelled, but otherwise you're not even giving a fair chance for 'let the buyer beware'.