So, let's say we have a project. For whatever technical (or social, historical, religious...) reason, C is chosen as the right language.
Why does that imply that the programmers on that project should therefore write that C code in a terminal, with no linter, code formatter, static analysis, test runner, etc.?
Eg while I enjoy understanding all the layers of software in a computer and am perfectly comfortable with vim and a makefile (although I prefer vscode and cmake), most of the other developers I work with are just as competent with C, but can't really function if they can't use visual studio. To them visual studio is the basic tool and vim+make are advanced tools.
That said, Vim has some IDE-like features, moreso for C (by default) than some other languages.
Again, the point is that C is complicated and hard to work with as you scale up into a bigger project, not that my tools are better than your tools.
Presumably they were busy generating billions of dollars of revenue.
Also, I'll add that automated testing was definitely not as much of a thing in 2003 as it is in 2023.
There are, of course, always exceptions.
Teams can use a combination of different IDEs and run the tools at different levels or their pipelines, which necessitate that they be automatable (and not GUI only).