This is an example of an incredibly important category of normative signs, namely signs that promote adherence to a mutually advantageous coordinative convention. Ignore the pictograms at top, forbidding wheelchairs, etc. Focus on the words at lower left and lower right.
It’s not clear that walking on the left side of the moving sidewalk, and standing on the right, is anything like a rule in the strongly prescriptive sense. It’s just a good idea. Everyone — walkers, standers, and those sprinting to catch their flight — benefit if the standers squeeze to the right, allowing those in a hurry to hustle past. Technically speaking, it’s an equilibrium strategy for a social coordination game.
In some places, this convention is taken for granted, part of normal social expectations. In other places, like an airport with international flights, a nudge is a good idea.