So it finally occurred to me after reading some of this that the reason Fahrenheit keeps hanging on (other than stubborn arrogant Americans) has nothing to do with precision. In fact, it's exactly the opposite; it has to do with imprecision. And--amusingly--it's because of base 10. Let's face it, most people, if asked to estimate the temperature, are not going to estimate to within one degree--either Fahrenheit or Celsius. You might have some super-savants who can tell the temperature to within 2 °C, but those are going to be few and far between.
But when we talk about the temperature, we don't worry about that sort of precision anyway. "It's in the low 50s" is pretty much as good as anyone ever uses or needs for determining what to wear outside. But "in the low 50s" Fahrenheit is a much smaller range than "in the low teens" Celsius. In fact, "the low teens" Celsius stretches over the whole "fifties" Fahrenheit. And since we humans, with our ten-digit set of upper appendages, like to group things into 10s, we'd rather have that group of ten be somewhat smaller rather than somewhat larger. That way we can say "Yeah, it's about 50" when it's 45, and those around us can't really complain, but it's much harder to say "yeah, it's about 10" and not get grumbles when it's actually 5.