Why can I not trace which retrieved document is responsible for what my AI just said?

Enterprise RAG systems retrieve documents from internal corpora, licensed datasets, and external sources and generate responses that blend retrieved content. No standardized mechanism traces which retrieved chunk influenced which output sentence. This makes copyright compliance guesswork, PII leakage from retrieved documents undetectable after the fact, and fulfilling GDPR Art. 15 subject access requests for AI-generated outputs impossible to do accurately. Training-time attribution research is advancing, but inference-time chunk attribution at production scale remains an open and unsolved problem with no agreed standard.