Strong Arguments for Unencrypted Networks?

- My neighbours can reassure me that I haven't downloaded malware, and vice versa?

- Parents can more easily monitor their children's viewing habits?

- Caretakers can assess whether the browsing activity for the elderly is normal?

- Personal data isn't "locked up" and purely entrusted to ISPs, companies providing services, and sophisticated criminals/intelligence agencies?

- Peer groups of friends and companions can verify that payments made by people are expected?

- Peer groups of friends can identify attempts to scam/defraud people?

- Archiving of societal activity over history becomes easier?

- It's more like the way reality is?

Edit: consolidating some extra items from previously-separate comments:

- Bonus side-effect: computationally less expensive.

- One significant/important drawback: authenticity and content integrity become harder to verify (although those can both be achieved thanks to cryptographic signatures within plaintext transmissions)