“The technology program required to close this gap would be remarkably circular, with no benefits outside the field of applied zero gravity zookeeping. The web of Rube Goldberg devices that recycles floating animal waste on the space station has already cost twice its weight in gold[49] and there is little appetite for it here on Earth, where plants do a better job for free.”

Ha. This rambling is entertaining but has little depth or vision.

These are not ‘valid reasons’ these are ‘arguably valid reasons made by cynical ramblers’ :)