Or it belonged to a dead relative and just found it.  Or they lost the Encryption Password to it and recently found it out.  Or they simply forgot and went through an old Computer only to find out they had Millions sitting in there.  Or it was a Computer some body found in an old garbage.  Many possibilities.  But I doubt they knew about it and had this much self control.  By the time a few Dollars turn into a few Thousands, you already contemplate selling.  Imagine Dollars turning into MILLIONS and waiting for over a decade until you finally sell.  Almost impossible, psychologically speaking if you ask me.