...it gives a bit of history and behind the scenes of something that is trivial to consume (book, website), but technical to produce.

My grandpa had his own printing company back in the day, and that was one of the the original broadcast technologies. Books, periodicals, businesses, menus, invitations, professional directories... they all filtered through one of the local printing presses.

Practically as well, you'd take a million individual letter pieces, arrange them into plates with pressure-fit clamps, then run 1000 (or more) copies of each page or whatever. https://en.wikipedia.org/wiki/Hot_metal_typesetting

For bigger runs, they'd "lock" the page into slugs (lines of text) or plates (full pages).

At the end of the job, they'd melt the plates back down, so the colophon could also be considered "hey, this is how you reproduce it for the second printing run... it was Garamond, not Baskerville, and 25% cotton paper, not bond."

In a way, the colophon contains the original spirit of open source, and "opening the HTML pages to see how it's done."