I think there were two reasons ... cost and maintainability. You could build a very dense circuit with this technology, but because the wires were continuous, it was very difficult to modify a circuit as required due either to a mistake or a design change. I knew one fellow who bought a bunch of this hardware at considerable expense, yet couldn't use it, ultimately, because it was too difficult to modify. He hadn't yet discovered that there were "two-level" wire-wrap sockets, so his wire-wrap boards required he skip a slot between boards, and that didn't work in his Apple-][. In reality, it's never necessary to place more than two levels on a wire-wrap pin. People do it, but it's never necessary.