The accuracy of recollection can certainly vary, but the point is that some information is retained long-term even when it isn’t made use of in the meantime. Of course one could argue that actually it is being made use of unconsciously, but I’m skeptical of that, given the relative irrelevance of the details that can be recollected. It’s also not that difficult to imagine that some memory-representing micro-structures in the brain just happen to be stable over decades even when they remain untapped.