Felicity wrote:
…how dare they destroy our paper reading pleasure.

I think the Tokyo Metro has run out of things to nag their customers about, so this poster is grabbing at straws.
(The Metro is avoiding bringing up the problem of people littering drink cans on the platform and in the train cars, which is an actual safety hazard when the micro-size 200 ml can-coffee get underfoot and passengers are so crowded together they cannot see the ground.)