[nucleardog]

> view whatever was hosted at that address (default host in the case of virtual hosting). Not sure why these websites do not persist.

You probably answered your own question here--I imagine at this point the amount of things on the internet that aren't using some sort of virtual hosting are quite tiny.

Even ignoring everything else, with the IP address exhaustion and the push for SSL (can't get a certificate for an IP address), websites available directly at an IP address just aren't really a thing anymore.