The advantage of imperial distance and old LSD money was the ease of using fractions.
So often in woodworking you want to halve something or divide it into thirds, or whatever, and twelve units to one bigger one make this much more convenient (OK, not dividing by five or seven, but honestly, that's rarely necessary).
In contrast, Millimetres gives you a good working unit for simple construction work.
Sheet goods are sized as they are for all sorts of reasons. The most significant during the 1970s was that MMB machinery made imperial sizes, and thickness was easier to convert than length and breadth. Metric sizes are still approximations to / substitutes for imperial, as we need those sizes for convenience. I can just about get 8'x4' sheet goods up and down the stairs in my house. 3m x 1.5m would be impossible.
Plumbing pipes: well, we started it! Our copper pipe was imperially-sized, but measured to INSIDE diameter, not outside. Metric pipe is OD, so 15mm comes very close to thicker-walled 1/2" copper. During the big changeover plumbers could interconnect by thinning-down 1/2" pipe with emery cloth. I did exactly that on one of the last pieces of 1/2" in the house, just before last Christmas 2016). If you ever do this, err on the side of a slightly sloppy fit in a 15mm coupler, otherwise you risk the capillary action not working and pinholed joints when the flux washes out.
Converters were also available for the lazy (I've got one somewhere, as a museum piece).
Because there's nothing usefully close to the OD of 3/2", 22mm was chosen as converters were more practical. I have a few of those and they're still useful occasionally. And anyway, dies (plugs) to expand pipework so you could make soldered, overlapping joints without fittings were pretty common, as it was (and still is) standard practice with lead, and plumbers expected to be able to do it. You usually have to anneal new copper pipe first (it's significantly work-hardened by the thin-wall extrusion process), and be very careful, as the walls are much thinner than they used to be. But you can still get the tools and they are very handy to make repair couplers.
Personally, I'm happy with both systems, but I like the human scale of feet+inches.
According to Wikipedia, the Metre was originally supposed to be equal to one ten-millionth of the distance between the North Pole and the Equator. The French (who foisted it on everyone else) decided this was in accord with God's cosmic plan (don't go there, please!). But they got the primary measurement wrong, and actually it's a nothing - an entirely arbitrary unit, and not very useful for all that. Imagine how bloody awful it would have been if they'd decided on something half as long again...
...at least feet and inches make human-sized sense, and have some correlation with horses' bottoms.
E.