>It could be that people ignore it because the rail network is asking you to break the social contract at no benefit to you whatsoever, only an increased risk of a negative encounter (at best getting cursed out and at worst how long until someone gets shoved for blocking the walking half?)

That won't happen. The OP clearly lives in Japan, probably Tokyo. That kind of thing never happens here; it's an American phenomenon, and probably various other not-so-civilized nations. Here, breaking the social contract in this way just makes people annoyed and gets you mean stares at the very worst.

Also, he's mainly talking about people walking up the escalator, not down. Many stations only have one escalator to the platform, and it's usually going up, since it's easy to walk down stairs.

Finally, it's only certain rail companies that have this policy; there's a bunch of different train operators.