As an American with a physics background, a while ago I casually reviewed how bad our non-metric system is -- http://joshuaspodek.com/metric-system-isnt -- and found it not nearly as bad as people treat it. Among other things, when I build things it's useful to divide in half a few times, which is easier with inches and feet. And I've found no benefit to Celsius's 0 and 100 coinciding with water's state changing. I b…
Pretty much the same argument for miles per hour vs kilometers per hour - 100 mph is all anyone's ever going to go during a normal day.
That's an interesting point about being able to divide by half more than once for feet/inches, though - I hadn't thought of that before.
(From another American with a physics background)