The SQLite project is much like SQLite itself, i.e. simple and as self contained as possible. Naturally this means they have to deal with the overhead of developing and maintaining a large portion of their toolchain. On the other hand they avoid the litany of problems that comes with using 3rd party tools, and those tools can be optimized for their particular needs.
> Who uses it outside SQLite team?
Tcl/Tk is the only big user of Fossil, as far as I'm aware.
Why should one use that simple forum instead of Discourse? Why should one use the simple wiki than say Wiki.js?
And of course the toolings are already way behind as in there's not a single GUI client?
And it doesn't seem to have any social login, so people have to create an account instead of using GitHub logins.
Who uses it outside SQLite team?