I used to have something like

  nmap ,w :w<cr>

in my vimrc so I can only press two keys to save the file. I think the colon character (:) adds a little overhead to such a common command because one has to press shift with the colon/semicolon key (depending on the keyboard layout), and then release them to continue pressing the remaining keys. And this is if you're already in normal mode; if you're in visual/insert mode you'd have to press Esc or Ctrl+[ first. Of course, these are small details that you don't normally think about, but it does feel a little cumbersome when coming from an editor where you can just press Ctrl+s or C-x C-s (in the case of Emacs) and continue working.

In the end, vim doesn't stop you from defining key bindings to improve your workflow.