In a way it is a bit sad though. It gives a more rigid feeling to things. "about quarter past" would usually be something between :10 and :20. There is room for interpretation and time feels more available with less demanded precision.
They are? I wouldn't talk about fractions of cm or km if I wanted to be precise, I would say 2,5 mm or 500 m. Half a km is approximate, for when accuracy isn't that relevant.
Yeah, imperial units are terrible. 1/3 cup nuts, 1/2 cup flour...
More granular units exist, but they're not easier to use and so no one does. The only reason anyone would refuse to switch to metric is because "it's always been done that way around here"