Well, the scale is just crazy. Somewhere (if anyone asks for citation, I will do my best) I've seen estimates that if we humans were to live as hunter-gatherers, the carrying capacity of the planet would be somewhere between 200-500 million - at most 1/16 of today's population. And pre-industrial revolution, the population stayed under 1 billion, which is probably a reasonable guess at a ceiling on low tech agri, with animal-powered cultivation. A regression to anything like that now would likely be even fewer people, given the prevalence of depleted soil, fisheries, aquifers, etc.
Politically, culturally....yeah, I have no idea if any current society is really going to exert maximum consumer force on agribusiness to do humane and sustainable meat production. Right now, it's just a niche, among many. Probably won't change until there's a crisis, or society evolves towards some kind of post-capitalism, post-oligarchy.
Or there's massive eco catastrophe, wiping out 9/10 of the population. That tends to get attention towards sustainability issues. If they don't eat all the historians before they can remind people how they got into that reduced condition.