I am retired now but during my professional career as a software engineer I never used an IDE to write software, I used vi/vim and the command-line toolchains for the language(s) I was using, even python, at the end. GUI programs like web browsers, spreadsheets, PDF viewers were also used, of course. So it is possible to develop software mostly on the command-line.

But I started when there weren't any GUI programs for developers, so it was easy for me. I do think that an experienced developer should be comfortable using the command-line but these days using one or more GUI programs in the developer toolchain is normal.

So, again, why?