Because those like me who don't install any of those apps don't have anything to share on HN. Showing that you have a nearly default desktop isn't interesting except when people are claiming that no one does that.
I completely agree. I have used macOS since 2007 and the only thing I have really used as an extension is Alfred in place of Spotlight (although nowadays I am just using Spotlight). I am very happy with the UI as it is (on Linux I used everything from WindowMaker, KDE, GNOME, to tiling window managers).
Also I have many friends and family members who use macOS and I think none of them have third-party programs installed to modify the UI. So, you won't see them posting here about the extensions that they use.
And Raycast actually has the Rectangle functionality built in, although I prefer the separate app, there are some ‘defaults write’ values I can change on the command line that I like (to give me a wider bottom margin on my screen - I stick Silicio in the corner of my screen for instance.)
