I do have sympathy for the elderly and for people trying to escort their small children and their luggage within the confined space. A few years ago at SFO I happened to be nearby and first to assist a woman who fell as she tried to exit the walkway with her walker. Fortunately she wasn't hurt.

Haven't you seen the sign at SFO?

Do not move while on the walkway. Stand toward the middle. Do not place hand luggage behind you. Traveling companions must stand next to each other at all times.

I haven't spotted it yet either, but I'm sure it must be posted somewhere.