Because way back, they standardized the outer diameter for lugs, not the inner for seat posts.

You consider that standardized? I'd say "standardized" would mean interchangeable between bikes and brands. When I began riding back in the 1980s it seems there were only a few sizes. Now, not only are sizes not standard, neither is the shape of them. One of my bikes has an aero CF seat post that fits only on that model/brand bike. Which really isn't a bad thing, per se. I mean seat posts don't really wear out like bearings, chains, chainrings, or gear cassettes. So, you don't really have to worry about them much. But IMO, I think seatpost sizing has gone the opposite of standardizing.

Dan

this, basically. And if you go back far enough there was no ‘standards’ for lugs or frame tubes, because most bikes were of course completely hand built and you had very few ‘large’ companies. It was mostly small companies building completely proprietary machines. Also, from roughly the 1890s through the 1920s or so, there was so much experimentation and new designs and technology, that it would have been damn hard to standardise, especially across Europe, when each company and each nation was always claiming the ‘best bikes in the world.’ I will agree that it took way too long to even just narrow it down. But this actually has a lot to do with the big tubing companies. (Reynolds, Columbus, Vitus, etc) as much as the big lug makers like bocama, prugnant, Vagner, etc.)

in short, it’s just complicated. There’s no simple answer to the question.

No. It's like the one in this picture.



Dan