Two reasons are listed: - DNS records - Cookies Both of these things seem to have been design with "www" in mind. So the reason boils down to: original spec

Two reasons are listed: - DNS records - Cookies Both of these things seem to have been design with "www" in mind. So the reason boils down to: original specs of various technologies are optimized around the assumption that your site will have a www (or more accurately: a subdomain rather than a naked domain). I find "www" aesthetically unpleasant. If one must use a subdomain, how about "web" instead? It's still three characters, but much cleaner.