If Piketty is coming from a Marxist or Marxist informed background, which may be possible given his nationality and academic traditions there, then it is not at all surprising that he consistently favored structural explanations to policy explanations.  

A key point in traditional Marxism is economic determinism, that the underlying dynamics of capital are the ultimate driver of history.  Politics is secondary.  This is, obviously, a point that has been greatly contested within Marxist circles, but it has never been rejected or conclusively disproven in any manner.  Now, that doesn't mean much, as proof and disproof in the realm of grand theories for all of human history is a somewhat intangible matter.  But still.