Air - 6:48 am on Apr 26, 2001 (gmt 0)

SSI is useful so that you can have a page with what looks like a normal html page extension, i.e. page1.html or page2.htm, etc.. and because SSI is imbedded in these pages they actually call a script to serve dynamic content based on the visitor's IP address, User Agent, or other header information.

Without SSI you would be forced to imbed the script in the page itself, making for a messier implementation, you can equate .html or .htm to .cgi but then plain .html pages won't work for whichever extension you equated to .cgi.