I was in a museum recently in Germany (Koblenz) that had a display of mostly silver coins, unearthed during a building project.
What's interesting is that researchers could figure out exactly what year it was that the hoard was buried - it was 1688, during a period of turmoil and war (attack from France). All the coins were fairly similar in age, and the latest was minted in1688.
I've come across this numerous times in musuems, and in reading historical texts. Hoards like these are buried during revolutions and wars, and forgotten. Or the person that buried them got killed in the bad times, and so they remained buried.
It shows up in literature as well. Samuel Pepys’ diary entry for 13 June 1667 records a request to his wife to bury the family’s savings in their Northamptonshire garden (the Dutch were attacking southeastern England). Though presumably they were dug up again.
Obviously the "inheritance plan" of the people that buried the hoards were not well thought out. Very likely it was a time of panic and confusion, lots of uncertainty.
I wonder what will happen with some of the "hoards" of bitcoin that current holders have. Do most people have well developed inheritance plans? I really doubt it.
Overall, burying coins was a practical response to the uncertainties and risks of the times in which people lived