It's not so much invoking it as it is asserting it for the record. By immediately saying "I choose to remain silent so that I do not incriminate myself, as is m

It's not so much invoking it as it is asserting it for the record. By immediately saying "I choose to remain silent so that I do not incriminate myself, as is my right codified in the Fifth Amendment", you are making a clear and conscious public affirmation that your silence cannot be used against you. But I don't disagree with you; I don't think we should have to voice our rights. We should be able to hold the government to the task of protecting those rights, rather than having to protect ourselves explicitly.