Plenty of people have, somewhat nullifying your comment.
On a finite planet with 8 billion people, to feed everyone the "western diet," we would need 2-5 such planets. It's simply not longer possible.
Veganism grows very fast, though. It's already starting to influence meat and dairy sales, enough to make some producers very nervous (wood milk ads, for example).
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https://www.youtube.com/watch?v=ao2GL3NAWQU
The Secret Reason We Eat Meat - Dr. Melanie Joy
https://www.plantproteins.co/vegan-plant-based-diet-statisti...
As many as 6% of U.S. consumers say they are vegan — a 6x (500%) increase compared to just 1% in 2014.
U.S. retail sales of plant-based foods have increased 11 percent from 2018 to 2019, hitting a plant-based market value to $4.5 billion.
This is one reason why the rise of meat-like alternatives that nevertheless taste like meat are one of the most subersively impactful ways of turning someone vegan. I suspect once we as a species transition fully to lab grown meat, we will all basically be vegan. But the reason why so few people are vegan these days (out of the overall human population) because it is simply less convenient than eating meat, given that we like the taste of meat. There really is no alternative currently that still satiates people's demands for the taste of meat.
I wish... there are many obstacles to implementing that on the scale and timeline needed. I worry we don't have time to wait for that, while we already have plants that could sustain us completely and easily (82% of calories, 63% of proteins).
https://ourworldindata.org/land-use-diets
> it is simply less convenient than eating meat
Tradition, culture, convenience, taste. The only reasons.
> There really is no alternative currently that still satiates people's demands for the taste of meat
It's starting to change. Plant-based alternatives for meat (junk food) are getting better everyday (at least where I live).
In the last years came new bacon and sausages, which my SO refuses to eat because they're "too meat-like".
Veganism will never save us there.
It's because meat tastes good. That's literally all there is to why we aren't all vegan. Humans will not voluntarily give up one of the nice things they currently have access to and enjoy. Nobody cares about delayed indirect consequences on a planetary scale. Our brains aren't wired to think that way, since it provides no instant gratification.
If someone came up with a novel way to create a meat-like material that actually tastes as good, without involving inefficient animal farming, it will be a much more successful approach at solving this problem.