Because you want a science advisor who is incapable of having faith in Science. And... they've been on this exact terror tactic for at least 50 years now.
In 1973, Holdren encouraged a decline in fertility to well below replacement in the United States, because "210 million now is too many and 280 million in 2040 is likely to be much too many."
Yeah, we passed 280m in 1999, in 26 years, not 67 years... less than 1/2 the time of his brilliant predictions. And, oh yeah, we are still exporting massive amounts of food, even at 330m.
Leftists revel in discussing massive population losses. Mass death gives them a warm glow. That's why all the greatest mass murders of their own populations have all been performed by Leftists.
Just drove through the California Central Valley couple of days ago and was floored by the bounty and variety of that landscape, every inch of it under cultivation, none of it “organic”. Many replantings of nut tree groves taken out during the previous years of drought. Kids should be taught that farmers are heroes.