Git itself uses this functionality. On my ubuntu system the path is `/usr/lib/git-core/` and in it you see all sorts of bins for "git commands", e.g `git-rm`, `git-mv`, `git-difftool`, etc. A lot of these are just links back to the git binary these days, but many features begin life as a standalone `git-$X` executable, and back in early git days much more functionality was split across executables. (The ones that are now links back to git are largely for scripting purposes, a lot of git "plugins" and various CI type scripts will call `git-mv` rather than trying to get quoting right around calling `git mv` for example.
It also helps make plugins easier to distribute. I don't want to have to type `git-x` sometimes and `git y` others, and if I want my plugin to get adoption, I really really don't want that. So things like git-lfs, git-annex, etc can easily be distributed, documented as a plugin, and generally be considered as "a part of git", rather than a separate command.
This pattern is also not unique to git. Other softwares have followed it, notably cargo.