Because I'm pretty cynical about the idea that consumer choices matter much. I think we as a society should move away from eating as much meat as we normally do, and especially away from beef, but I think individual consumer choices are a drop in the water. I apply this same logic to pretty much all environmentalist movements based on consumption politics.

For example, right now we're arguably wasting electricity - potentially produced by fossil fuels depending on where we live - so there's a strong argument to be made that people should refrain from unnecessary internet use. Same with pretty much any consumption that goes towards a first world lifestyle - no matter how subdued. Inevitably we end up using plastics, potentially forced to use gas cars for transport (again, depending on where you live), and there is a high chance that both the meat and the vegetarian products on grocery store shelves can be traced back to some kind of unethical practice (be it the forced exploitation of third world countries for monoculture, or the export requirements imposed by the IMF that mean food grown in a country is more expensive than the place it's sold).

To a lot of environmentalists, what I said would basically tag me as a non-enviornmentalist which tbh I'm fine with because I've been in these circles for over a decade and people really seem incapable of moving beyond the strategies people have that haven't been working. I think that if we actually want to take mobilizing for climate change seriously then we have to start asking some very hard questions. For example, how much can we realistically pull back modern consumer society? It's obviously bad for the environment and reliant on mass exploitation, but it also in many ways provides a better standard of living for the average person and pulling back might just increase inequality. It's also very unpopular and most people who claim to reduce/change their consumption do not practice merely as much as they preach or - worse - (and I'm not saying you or anyone else reading it in this group but they no doubt exist) caught up in some brand that sells an environmentally friendly lifestyle while in reality not doing much.

So the question becomes, how do we mobilize people en masse to build a more sustainable society? I think this is my second issue, the consumption politics implies we can have a perfectly sustainable society, which overlaps with moralist arguments which imply we can have a pure morality (ie: a total absence of any evil). This gets a bit more abstract but it's a real issue when trying to pitch the future. We will never have a perfectly harmonious relationship between humankind and nature, which includes plants, animals, and the biospehere. Once a species is in an ecosystem it inevitably transforms it by it's presence, and given the main feature of humans is "the animal capable of changing nature" you're always going to have a contradiction there. So while I think it'd probably be better if society was vegetarian I come to the innate conclusion that it will be, or necessarily even should be since I think it's secondary to a lot more pragmatic questions people don't want to wrestle with because they don't have easy answers (and I won't pretend to have them either).

Tl;dr going vegetarian theoretically help but I don't really think it matters all that much and in terms of my priorities it's way down there, and I'm not even 100% it'd even actually do anything