The brains of infants and very young children are capable of storing fragmented memories, however. Such memories cannot be explicit or deeply encoded, but they can nevertheless have influence. But such unconscious memories, even though pervasive, are not quite what Freud or Jung meant by the unconscious. Implicit memory may be far more mundane than Freud's dynamic 'unconscious mind', but it is more significant since it reaches into every aspect of our lives. Most lost memories are lost because they were never elaborately encoded.
Perception is mostly a filtering and defragmenting process.
Our interests and needs affect perception, but most of what is available to us as potential sense data will never be processed. And most of what is processed will be forgotten. Amnesia is not rare but the standard condition of the human species. We do not forget in order to avoid being reminded of unpleasant things. To those whose lives are devoted to getting into the unconscious mind, either to find out why they have problems or to find some transcendent truth, I say you will be looking for a long, long time.