I read the edits on your original comment. I think you’re missing the point that the metric system at least scales in a reasonable and expected way, which is not the case in the imperial system of measurement.

And to your point about averaging a human arm and using that as a measurement standard, no, it’s not necessarily better. You still need an exact standard that you have to measure against for any kind of precision. Making it similar to the size of a human body part doesn’t matter unless you’re estimating, which isn’t how anything is built anymore.

There are reasons the old standards were abandoned.

Hard disagree. There is far too much variability in the body size of adult humans, especially when taking sex into account. Sure, maybe my foot closely resembles the foot-size of said monarch but my 5 ft tall wife’s doesn’t.

There’s no reason to use body paste measurements for nearly any purpose in the modern day. You can’t build a house based on the rough size of someone’s arm when you have half a dozen people minimum working on a project. You need a standard unit which would need to be measured using a standard unit measuring device. Either way you need to use a measuring tool, so why not use a standard that makes the math easier.