"A yard is the distance from your sternum to the tip of your outstretched hand."
According to folk belief, it's the distance from the tip of Henry I's nose to the end of his thumb. According to an early definition, "It is ordained that 3 grains of barley dry and round do make an inch, 12 inches make 1 foot, 3 feet make 1 yard."
Who here has an idea of the size of a grain of barley dry and round?
At 39.3 inches, a meter is just slightly longer than a yard, and for "traditional purposes" where the sternum/fingertip approximation is good enough, a meter and a yard can be used almost interchangeably.
Somehow all those people using metric in their daily lives don't feel like they are missing something special by having "ancient, organic" units. (BTW, at what point does something become "ancient"?)
"Or don’t bother, because the definition completely changed in 1960"
The yard definition 'completely changed' in 1959, when it defined as exactly 0.9144 meters. Before then it was different in different countries.
Since the yard is pegged to the meter, this means that the yard is now legally defined as the time light travels in 1/274130223.5952 seconds.
"The first third of the 20th century, for instance, saw some quite serious efforts to rationalize our systems for dates and times."
As well as the 1700s, when France ran under a rationalized calendar, which provided the name for the Thermidorian Reaction. This is part of the same movement that brought us the metric system, so I think it's odd to exclude that very serious effort.