I am really unclear what the real purpose behind this decision is.

At first glance I thought about the positive aspect that it might incentivize and diversify the PvE game a bit.  Then I considered the free-market implications.

I don't follow the market much but it seems that the supply / demand dynamic with kernels will be widely skewed.  First because its easier to farm the lower kernels and obtain significant quantities.  This then causes a high supply, low demand equation which lowers the average price.  Meanwhile the opposite happens for the higher tier kernels.  The supply is virtually cut off so the demand will be astronomical.

The free market relies on scarcity to generate a profit margin, however extremes of supply and demand ultimately ruin a free market economy from the inside out.  Therefore we have governments to control the gouging and monopolizations / exploitations. 

The devs just legalized the black market, as it were.

From the perspective of the drop rate nerf.  I believe that is purely a business decision.  They wanted to slow down the game progression and research is one of their biggest throttles.  Welcome to research on cruise mode.