It's just London especially has been around for so long that this sort of stuff just accumulates. The charity that exists purely to help look after just the Thames crossings in London that was doing this is itself almost 1000 years old for example. There is lots of old stuff - it's just part of life, not something that people go out of their way to give a shit about.

As a British person who was involuntarily dragged around countless ruined Abbeys, castles, and monestaries for hours as a sprog by my parents, I can assure you that there exist plenty of British folk with an active disinterest in "old stuff", as you put it.

It’s also illegal to tie a giraffe to a telephone pole or street lamp. In another city it’s illegal to eat fried chicken with anything but your hands.

It is true that British people do make more of their identity about it, and they tend to ignore _really_ old stuff (i.e. most of the quirky stuff is Victorian, not _that_ old).

(disclaimer, am British)