So when do we get trickled down on exactly?
It's just not necessarily money that's raining down on our heads.
Less snarkily: Piketty observes that reinvested capital accumulates at a faster rate than labour. Also, we have no global taxation system, so capital flows through the cracks into regimes with the lowest tax rate -- meanwhile, labour is pinned down by strict laws restricting immigration, and mostly can't go where wages are higher. (In the tech sector we're privileged exceptions, but consider the plight of an agricultural labourer.)
The system itself is broken, and the people who run it have forgotten the lesson of history that people with no stake in a system eventually turn to violence when threatened with starvation.