After learning a language -Why can't anyone go back and narrate what and how one experienced during the first year?

It will be interesting to explore the reasons that fill the "gap of inability" between the most efficient language learning phase and "culture bound listening phase" as Patricia says . After learning a language what prevents one to go back and bring insights, describe from that efficient learning phase in one's life. Being convinced that these insights / description once known will be objectively measurable as well. It seems the challenge in using MEG has a bias. Thus - what are those factors that prevent one to go back and recall the baby experiences while a language gets learnt - it may add new vocabulary or use existing words in a new perspective to share with others.