[eru]

Vim uses a similar paradigm of leveraging an operating system for editing. But it leverages Unix instead of coming up with its own half-baked OS.

(Disclaimer: I do use Emacs, mostly.)

[ralph]

Exactly. Emacs didn't start on Unix IIRC and seems to prefer to have everything built in. vi was created by Bill Joy on Unix and wanted to work with the rich language of shell commands from the start, as ed(1) did, so it concentrated on editing text well and integrating with Unix well. To see some Emacs users you wonder why they're even bothering to run on Unix. ;-)