There are literally millions of Americans (probably everywhere, but I mainly practice medicine in the US) with chronic back problems who can't stand for long periods of time, though many can walk much farther/longer. Also many people with ENT problems like Meniere's disease, or abnormalities of the cerebellum in the brain will have problems with balance and often with prolonged standing.

I've traveled home to Seattle through Amsterdam on KLM and Northwest and have endured the endless security screening lines, but they weren't forcing the shoe carnival as recently as last May. Is it a DL thing? OTOH, just returned from TLV through ATL on DL, and they didn't require the shoe carnival in TLV. However, they wouldn't let us buy any liquids over "3 ounces" at Duty Free, even if we promised to put it in checked baggage once in ATL.

Consistent inconsistency to keep us fooled.