Em dash in vim

I'm always frustrated about writing --, instead of – for en dash in vim, but using digraphs can be bizarre. Why haven't I thought earlier about making it a keybind, just as in most today's editors (LibreOffice, MS Office, etc)?

inoremap <buffer> --<space> –<space>

• https://vi.stackexchange.com/questions/2199/what-is-the-easiest-way-to-insert-en-dash-in-vim