That's true on the current margin in the US but only on the current margin. Creating one more pound of beef than we currently do does require a lot of farmed soy and other crops and ends up very inefficient. But there's also a lot of grazing land in the US that can't be used for intensive agriculture and provides a lot environmentally "free" (minus methane emissions) meat. From an environmental standpoint we want to halve or so the amount of beef we consume, not eliminate it entirely.

And other countries than the US are operating on differnet margins.