>>717602191 (OP)
The world has been through several wars in the meantime. There are area's around the globe that are nuke zones, biowarfare zones etc, where humans cannot enter but the servers are still running. Hong Kong and South Korea I think are two such places where bio weapons have made them uninhabitable but their geo power stations even though unmanned keep the computers running.
It's worth noting the old net which is just our net today is still there. AI's can freely move around from place to place across continents and cities outside of the blackwall so there are always places to escape to as long as the servers do not have the blackwall protocol either because the servers were made before the data krash or because corps are doing nefarious shit.
For instance in Hong Kong the corporation Kang Tao has allied with Alt to create an AI city in the net for engrams to congregate for some unknown reason.
As to why they don't go around and secure these areas, it would be almost impossible. AI can freely move anywhere outside of the wall, across continents, hibernate in unsecured data terminals or other shit but even worse, the AI that live beyond the wall have been constantly evolving and getting stronger which means dealing with them is incredibly dangerous.
But the real answer is what the Netwatch agent in Pacifica tells you. Corps and the world public as a whole think the AI problem beyond the wall has been solved by the creation of the Blackwall and Netwatch tell people nothing can cross it. This is generally true. But of course there are ways. The voodoo boys manage to send you across somehow and the NUSA has secretly created a cyborg who can just open holes in it at will.