Left or Right?

If you take a close look at the picture taken at Phoenix Skyharbor airport, US, the freewalk way on the left side of the escalator, people habitually walk on the right side. However, the sign hanging down from the ceiling is clearly warns/guides people to 'Walk On Left, Stand On Right", which is aganist people's daily behavior routine/habit. Even just passing the warning sign, people still naturally Walk On the Right (as seen on the picture). If you have ever experienced this escalator, you will probably agree with me that when you do walk on the left, it is awkwardly user unfriendly to have someone pass by on the right. To make the experience worse is when the person is pulling a luggage.

Update: on my recent trip to Japan, surprisingly I found that the sign guides customers 'Walk on Right, Stand on Left'. Unfortunately, I didn't get a chance to take a picture of the sign.

Update:
My friend, Dr. Hana Smith, gives me the following helpful and insight explanation.
I have to say, it does make sense! But when you are near airport next time, try it out and tell me which way you feel more pleasurable/comfortable, i.e. "walk on left, stand on right", or "walk on right, stand on left".

" The 'Walk On Left, Stand on Right' refers strictly to the escalator path, and follows the same convention freeways and interstates follow. Except instead of 'slower traffic keep right', it is 'standing persons keep right'. Either way, faster or moving traffic pass in the left lane of the highway (cars)or walking on the left side of the escalator (people). "