They're adhering to their charter. If you show up to my manager demanding to know why I made a specific engineering decision, he's not going to tell you - that's not the process, that's not his job, he's going to trust me to make good decisions unless presented with evidence I've misbehaved.
But as has been pointed out elsewhere, the distinction between the Dual EC DRBG objections and here are massive. The former had an obvious technical weakness that provided a clear mechanism for a back door, and no technical justification for this was ever meaningfully presented, and also it wasn't an IETF discussion. The counterpoints to Dan's engineering complaints (such as they are) are easily accessible to everyone, Dan just chose not to mention them.
But as has been pointed out elsewhere, the distinction between the Dual EC DRBG objections and here are massive. The former had an obvious technical weakness that provided a clear mechanism for a back door, and no technical justification for this was ever meaningfully presented, and also it wasn't an IETF discussion. The counterpoints to Dan's engineering complaints (such as they are) are easily accessible to everyone, Dan just chose not to mention them.