It’s not really about convenience. The vast majority of humans simply can not afford to carry the personal cost of avoiding the negative externality of their meat consumption.

That is to say, the vast majority of humans can not afford to sacrifice not eating meat to get their protein, due to a combination of inavailability of suitable substitutes of equal or greater quality, and also the perceived quality of life sacrifice, the associated mental, emotional, and social costs of doing this.

For people whose diet and indeed lifestyle is established in part as being meat-eaters, switching is costly in more ways than just financial. And even if a theoretical diet could substitute for the missing meat which costs the same or less, in practice a satisfying entirely non-meat diet for most meat eaters would be expensive in time and money to achieve.

It’s not clearly an ethical win to demand all of humanity to pay the cost to switch when a better alternative is possible; go out and do the fantastically hard work of inventing a better non-meat. So good that it’s not a cost but a benefit to switch to it. And then (almost) everyone will.

I see huge parallels between this and, for example, electric vehicles. Forcing everyone to switch too early is extremely costly. But through technical innovation practically everyone will drive electric because it’s so much better for them.