When supermarkets started selling loose items by metric rather than imperial weight, Tesco initially put up signs saying that you could now only *ask* for items in grammes rather than ounces. There was lots of guff about "which is easier to say - an ounce or 28 grammes", but that rather missed the point. When you ask for "four ounces of boiled ham" you don't mean "exactly four ounces, to three decimal places". You mean "about 4 ounces - add slices until it's either just under or just over". And on that basis, you wouldn't ask for "113 grammes" (the exact equivalent). You'd ask for the nearest round number in that measurement system - 100, 120, 150 grammes or whatever.
I'm old enough (58) that I was taught (parents, grandparents, primary school) imperial rather than metric as my "folk units" - for everyday use. I know my height in feet and inches, and my weight in stones and pounds, whereas I don't know them in the metric equivalent. I estimate and judge in imperial - "it's about ten feet away". But I always measure in metric, for ease of calculation. And for me, ease of calculation is *far* more important than whether the units are "human-sized". The only change I'd make to the metric system is to make the base units for measurement the centimetre (ie give that distance the simple name "metre") to avoid the multiple syllables of "centimetre" for the human-size unit. Or else invent a new, single-syllable name for the centimetre.
I'd also make it a hanging offence (!) to pronounce kilometre (KILLoMETre) as "kill-OMMi-TAH" ;-) That really gets my goat, because the "folk" pronunciation is different to that of every other SI unit and SI prefix: MIcro, MILLi, KILo, MEGa, and SEcond, MEtre, FARad, AMPere. The only exception I can think of immediately is becquerel - and that's because it's his name. It's amusing to hear scientist-presenters such as Brian May. They switch between the two pronunciations, sometimes in the same sentence: evidently the director has said "pronounce it the popular way" and they usually remember but sometimes instinctively revert to the scientific pronunciation.