Given that productivity growth was slow for most of human history, it seems more appropriate to ask why it was so fast for a while. I keep thinking it may have been that manufacturing precision reached a point where we could drink a couple centuries of scientific milkshake.
In the middle of that sentence I was expecting a "low-hanging fruit" analogy, then you blindsided me with a milkshake.
That's not a good thing to be blindsided by.
SIAI benefactor and VC Peter Thiel has an excellent article at National Review about the stagnating progress of science and technology, which he attributes to poorly-grounded political opposition, widespread scientific illiteracy, and overspecialized, insular scientific fields. He warns that this stagnation will undermine the growth that past policies have relied on.
Noteworthy excerpts (bold added by me):
In relation to concerns expressed here about evaluating scientific field soundness:
Grave indictors:
HT: MarginalRevolution