A common convention with system administrators is to have the canonical name at www.* and redirect www-less requests to the former. If you argue that a browser implementation should fix uncommon configurations, I would argue that administrators should fix their configurations in the first place.
You don’t have this issue at all for domains that don’t have a www subdomain.
Furthermore it would be extremely confusing to have different content for www.example.com & example.com.
You don’t have this issue at all for domains that don’t have a www subdomain.
Furthermore it would be extremely confusing to have different content for www.example.com & example.com.