Because files and directories make up the core organization and architecture of any project.
Obviously when I'm working with 1-5 files then Neovim is great, but it's awful when I'm working on a real project with dozens of directories and hundreds of files. I can't hold that much contextual information in my head to simply remember the correct file name (or function name) and hit some keyboard shortcuts to jump to it. I need to actually see it all together.
VS Code's project tree and tabs system works great for me to always understand where I am working, and I don't have to remember any keyboard shortcuts to navigate.
I'm looking forward to some kind of open source VS Code killer with vim editing and native platform builds.