[skeaker]

Because it relies on the majority of the population to unanimously change their mind and diets. Between economic reasons (alternative diets can be more expensive to a family that has no time to cook every meal), health reasons, traditional reasons, societal conceptions, and downright stubborn people, it's essentially not possible without multiple generations worth of effort. That's much less realistic than changing mandated farming practices which could be done in a matter of years.

[exdsq]

Cows in world := 1,000,000,000

Seaweed per day per cow := 0.085kg

Seaweed per year per cow := 31.025kg

Seaweed per year for cow population := 31,025,000,000kgs

Global seaweed production := 6,350,293,180kgs

So, we'd need to increase seaweed production by 5 times. We would then need to distribute this from the largest producers (China, Japan, Korea) the countries that consume the most (Europe, US). This isn't a problem that can be solved by mandated changes in a matter of years, and I have no idea what the CO2 output would be for this sort of production and shipping.

[drooby]

Solid answer..

None of this needs to be binary this or that though. We can limit or eliminate our intake of meat products through personal choice AND engineer solutions to minimize environmental harm. We can do both and it does not have to be unanimous.

Also, there absolutely is a very real cultural shift happening right now that is embracing flexitarian/vegetarian/vegan diets.

[sam0x17]

While the term "vegan" has seen a rise in popularity, "meat" and even "steak" have seen a more significant rise in the last 10 years: https://trends.google.com/trends/explore?date=all&geo=US&q=v...

I also don't have data on this, but I think there has been a much bigger rise in performative veganism than actual veganism. For example many popular twitch streamers say they are vegan, and then the next week viewers point out they are eating a cheeseburger on stream and they'll say "well I'm not today obviously".