The reason why we (collectively) don't learn from history is that we don't live long enough to remember it.
Those alive today who are old enough to have actually experienced, as thinking adults, the Carter, Reagan,Thatcher administrations and the ascendancy of the ideas of Friederich Hayek and Milton Friedman - leading to the widespread discrediting of Keynesian economics - are in the ineffective minority. The knowledge that counts for economic policy is very much based on actual experience (you had to live through it); it is tacit in nature, very difficult to transmit to someone who did not share the experience. Written history is a pale substitute for the real thing, and it frequently distorts.
So, every generation seems doomed to find out for itself what it should not do by doing it again - just like every child in the process of growing up.