I think you asked a decent question in a convoluted way. You see vegetarianism and veganism as potentially anticapitalist. And you see Lemmy and other places being very anti capitalist, anti consumption. So why isn't your avenue of anti capitalism favored in these places?
Well I mean one obvious way is that piracy is a way to have your cake and eat it to. If I could be vegan, deny corporate interests of their money, and also eat "meat too", wouldn't that be more appealing than the traditional method of veganism where one must sacrifice some food options in order to have an affect?
Meat eating is deeply ingrained in our culture. It's highly subsidized and therefore relatively affordable. Toxic masculinity and other default mindsets make it omnipresent....
Short answer? Idk.