My attempted summary: it's mostly a matter of the window layout in VC6 giving the most real estate to Just Code, and also the hotkeys for common workflows (e.g. show/hide debug output) are simple.
Commentary: Modern MSVC tends to be more difficult to customize, whereas e.g. Jetbrains IDEs are more straightforward to customize in such a way as stb would be familiar with -- but, both MSVC and Jetbrains suffer from such awful performance (e.g. input latency) that it detracts from their usefulness as IDEs.