Because a little Vi is better than no Vi. Seriously though, I have used quite a few Vim emulations in several editors and I find them very useful (VsVim, Evil,

Because a little Vi is better than no Vi. Seriously though, I have used quite a few Vim emulations in several editors and I find them very useful (VsVim, Evil, ViEmu, Vintage...). In fact, I think of this 'embeddability' as one of the major features of Vim. I can use Vim key bindings in Visual Studio, Eclipse, Sublime Text, Emacs... all this very much improves the value proposition of learning Vim.