Because I don't want to look at 243.82cm on my tape measure, or if I am trying to lay something out to match the 16 in on center studs 40.64 cm, 81.82, 121.92,

Because I don't want to look at 243.82cm on my tape measure, or if I am trying to lay something out to match the 16 in on center studs 40.64 cm, 81.82, 121.92, 162.56, 203.2, and then 243.82 cm. For new stuff you could probably cheat and just base it on 40cm, which would be fine and perfectly acceptable, but for the old stuff which is still out there over the 8 feet, I'm already off by more than an inch which is enough to not hit the stud. Most framing isn't great, but still the error is additive and fractions are hard enough to work with that I'd want to avoid it. I think the transition for lots of things really has an additional cost. Is that speed limit sign metric or imperial? Sometimes its obvious, other times not, and there are thousands and thousands of different governments responsible for them.