Why does k8s secrets need to be base64 encoded when configmaps does not?

Secrets can contain binary data (the type is map[string][]byte), and byte arrays are base64-encoded in JSON serialization.

ConfigMaps only contain string data (the type is map[string]string), so the JSON serialization just outputs the string.

In 1.10, ConfigMaps have a new binaryData field that allows storing binary data, which is base64-encoded, just like secrets. https://github.com/kubernetes/kubernetes/pull/57938