I think he is guessing that the grandparents thinks that www or 'world wide web' means 'the internet' and should be root.
But actually 'web' reveals to the graph of hyperlinks between http/html pages that let you navigate from page to page, server to server. www denotes the host is primarily a http server serving web pages.
You could argue it's superfluous these days - if you are typing it in an address bar, you hope it is a http server, and if you are typing it in a ssh prompt, you know it's your ssh server. People add it because it's a convention and some users might get confused if you don't... (it's probably a vhost anyway most of the time)
It does have one benefit. www.google.com has its IP served from google's dns servers, whereas google.com comes from com's. Google does lots of dns-based load balancing that com doesn't support.
com. only serves the nameserver (NS) addresses for example.com., and if they are within the same domain, their IP addresses. It does not serve the rest of the records for example.com.
You can see this easily with e.g.:
dig -t any google.com. @a.gtld-servers.net.
vs.
dig -t any google.com. @ns1.google.com.
There is no real advantage of having it be 'www' coming from DNS...
There is a somewhat more modern problem which is that having a domain be a CNAME (the DNS equivalent of a by-name redirect) means it can't also have MX records and receive mail; the CNAME also ends up "redirecting" everything, including MX lookups. So if your web host offers yourdomain.someawesomehost.com and you decide to point yourdomain.com to it via CNAME, having you@yourdomain.com doesn't work unless yourdomain.someawesomehost.com is configured to receive mail for yourdomain.com.
