The foot is convenient for more than just human scale things. The speed of light is 1 ft/ns to within 2% and the speed of sound in air is 1 ft/ms to about 12%.
Both of these are just as easy to remember.
ft/ns and ft/ms seem pretty useless to me. I guess they work for room-sized things, but go outside and you're converting to miles anyway.
The simplicity of remembering 1 foot is utterly drowned out by trying to appreciate what a nano second is.
As a factoid it's easier to remember yes. But a factoid in isolation is useless. So unless you're going to do E=MC2 in imperial