In default httpd.conf it reads "as the standard dictates that a page is in iso-8859-1 (latin1) unless specified otherwise". Well, at http://www.w3.org/TR/html4/charset.html#h-5.2.2 it is said ""user agents must not assume any default value for the 'charset' parameter". So, server admins should always set default charset.
This is basically bug 23421. As for "the standard", Apache serves HTTP (rfc2616, though I think the comment you refer to goes back to rfc1945). The W3C's HTML spec has nothing to do with it. *** This bug has been marked as a duplicate of 23421 ***