Unencrypted networks can be easily intercepted and attacked. It makes life of an attacker a LOT easier to manipulate ANYTHING you receive and send to the other parties in the network.

Given the modern examples of how information systems can affect people's mental health, I think it's reasonable to assume that an unencrypted network has the potential to be quite dangerous to anyone that happens to come under attack.

EDIT: many reduce the role of cryptography only to conceal information. Rather, perhaps even more important and widespread use of cryptography is in guaranteeing information integrity and trust in third party's identity.