You sent me down a freaking rabbit hole, thanks! :)
From what I found is that there is the simple reason that the weird ones are distance, time and weight - the rest I looked into are based on formal non-normalized definitions (including lumen, which surprised me).
My guess is that in depends on where the unit comes from: science or day to day use.
I learned about the Siemens, the Weber and the Gray on the way.
Thanks again!
This is a proposal. Why does the article write as if it's a fact?