Why aren't collaborative mapping and local history sites popular in Anglosphere?
When I was reading “The Mystery of the Bloomfield Bridge” two months ago, one thing seemed a bit strange to me. It was the absence of initial clues on the Web about such a big local object.

You see, I am spoiled by the fact that almost everything notable in my area (up to, but thankfully not including, doghouses and poles) has been placed on a map or discussed somewhere. Say, there is a seemingly useless bridge right next to the one for the city road. What's that oddity? Well, you simply check Wikimapia:

http://wikimapia.org/#lang=en&lat=59.863328&lon=30.260704&z=17&m=w&show=/14300076/ru/Мост-под-путепроводом

Now you have enough pointers (in this case, including a Wikipedia link) to learn that it was a track for the first electric light rail in the country (early 1900s), which was then converted to a tram line, which, in turn, changed its course 45 years ago when a tram overpass was built nearby. If you want, you can check the overpass page, find a link to technical assessment stating its original construction errors and subsequent maintenance, and so on, and so forth, in the same manner you can browse Wikipedia articles endlessly.

Then you can study old maps, and compare them to the current state of the area.

https://retromap.ru/%D0%A1%D0%B0%D0%BD%D0%BA%D1%82-%D0%9F%D0%B5%D1%82%D0%B5%D1%80%D0%B1%D1%83%D1%80%D0%B3

https://retromap.ru/14197213_0420092_z16_59.863290,30.260446

Then you can study old photos, located and dated as precise as possible by community having a vast knowledge of old car models, construction dates, fashions, street decorations, etc.

https://pastvu.com/?g=59.863514,30.260703&z=17&s=osm&t=kosmosnimki&type=1

Then you can visit various forums to find discussions like “This small odd parking bay was used by trolleybuses to turn around when it was the end of the line at the last city block built at that time”, “That lawn may one day be the foundation of the proposed overpass”, “They still want to save this empty lot for the metro station. Maybe next century, lol”, “Nothing will or can be built here because of the gas pipe, look at the markers that prohibit any earthwork”.

In addition, there is a catalogue of all notable buildings in the city (resulting in each one in the historical centre getting a page) with sourced citations about their histories gathered from official documents, phone books, old newspapers, memoirs, etc.

https://www.citywalls.ru/search-street11.html

Note that those are all non-commercial projects carried on by their (interlaced) communities.

Their coverage of the West is much lower or almost non-existent. Of course, OpenStreetMap does exist, but there you can't add a note to some building to state that half of it collapsed 30 years ago, and was rebuilt. Moreover, Wikimapia has already gathered almost two decades of photos and data on small and big city changes, which itself is historically valuable.

Let's say I'm following John Hollingshead's journey in the sewers constructed on the path of River Tyburn in “Underground London”. I would expect everything mentioned in such a well known source to be placed on a Wikimapia-style site ages ago. Instead of that, I find various blog posts and articles with contradictory information, and some ad-hoc static and dynamic maps. For example, where did the author cross Regent's Canal? Some mentions say that sewers travel under Regent's Canal (the whole point is that they travel over it). Some say that they used Charlbert Street bridge (it is indeed thicker than usual — especially for such narrow footbridge — to embed the pipe that once provided moving water — or maybe “liquid” — for the park lake, but the sewer in question is inside much bigger Park Lane bridge). Some say that Tyburn flows inside Macclesfield bridge (one look at which is enough to see that it is impossible). Easily accessible interactive map would solve all of that for everyone.