Not that I don't agree, but they probably just decided it was more work than it was worth. It hardly seems like it, but if you sit down and count them up, there are already hundreds of NPCs in various towns, hamlets, etc. Going through and adding new dialog or reanimating them would be a horrendous undertaking. I too would love to see some actual reaction from the NPCs, but given how much work it would take, probably for the best that they focused on ARR instead.