Encryption is not popular in the current V2X pilot deployment because most applications are designed to share status to all nearby vehicles. Most of them utilize digital signature technology to prevent tampered or fake messages. Digital signature has following characteristics,
A message applied digital signature is not encrypted, so the content still can be read and you can decide to trust it or not through the verification of the signature included in the message. Besides, a certificate is the container of keys which could be used for encryption or digital signature, so certificates are always required no matter which one you choose finally.