[ugmtcbco] History is power

The obvious: The ability to look at someone's past gives you power over them.  The ability to prevent someone else from looking at your past helps maintain power.  Document this going on in practice, and the mechanism by which power is used or lost.

Speculation: what of the ability to look at your own past?  It is important, for you can learn from your mistakes.  But it's nontrivial to look at, and analyze your past.  You might not have the resources to keep records, the tools to analyze them.  The records might be owned by someone else (who wants to sell them back to you, for a price).