I only live in Metric-using country and I have no slightest idea how tall is five foot, whereas 155cm instantly comes to my mind as, ah, at around my eye level. It's all about familiarity.
Sure, but that's 3 digits versus 1; if the requirement is to express common, human sized-objects with rough accuracy in as few words as possible, it works just fine. Really, it's all semantics (as you say), but there are specific cases where one might be a better fit than the other. It's the inconsistencies in imperial that are truly horrible, not the arbitrary standard unit...
It isn't, really. If asked about my approximate height, I'd say 'eins-achtzig' ie 1.8m (notice me omitting the unit), which in practice also has only a single significant digit (or 2 if you account for tall people) and to me isn't any more unwieldy than '6 foot'.
How about 5ft7 vs 170cm. The later seems easier to express to me. If only rough accuracy is required then you only really need to take note of the first two digits. Incidentally converting between the two is quite messy; first you must learn that 1ft = 12 inches, then multiply the 5 by 12 then add 7 then multiply by 2.54. Where as to convert a metric figure to imperial, it does not matter so much whether you are starting out in metres or centimetres.
