Not at all. It makes sense to allow it, but never makes sense to require it.
"Why should the machine pointed to by the bare domain be the web server, instead of for instance the FTP server or the Gopher server?"
We use ports to distinguish protocols. A more salient question is: Why should there only be one web server in a domain?
In fact, it used to be common to have dozens of web servers on differently named hosts in a domain, all of which might be running several internet servers like http, ftp, etc. If you're actually old-school you'll remember knowing the names of individual machines at a site and visiting urls like http://foo.building.company.com
There are some technical reasons why you might not want your web server's A record in the @ for a zone, but they mostly no longer apply.
Not at all. It makes sense to allow it, but never makes sense to require it.
"Why should the machine pointed to by the bare domain be the web server, instead of for instance the FTP server or the Gopher server?"
We use ports to distinguish protocols. A more salient question is: Why should there only be one web server in a domain?
In fact, it used to be common to have dozens of web servers on differently named hosts in a domain, all of which might be running several internet servers like http, ftp, etc. If you're actually old-school you'll remember knowing the names of individual machines at a site and visiting urls like http://foo.building.company.com
There are some technical reasons why you might not want your web server's A record in the @ for a zone, but they mostly no longer apply.
www has never, ever been required.