Veganism is about exploitation, not suffering. The standard definition of veganism (from the Vegan Society) is: “a philosophy and way of living which seeks to exclude, as far as is possible and practicable, all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose.”
Suffering is incredibly hard to measure or compare. One person’s suffering metric can lead to wildly different conclusions, including eugenics, forced sterilization, suicide and a bunch of ecofascist nonsense. Most vegans reject this, but the fact that they’re utilitarian conclusions that can be drawn from a reduction of suffering shows how slippery suffering-focused ethics can become. You can’t directly control how another being experiences suffering. That makes suffering a shaky foundation for universal moral rules.
Exploitation, by contrast, is something you can control. You are the one doing the exploiting such as using an animal for food, clothing, entertainment, or labor. You can choose to stop. You don’t need to measure the inner experience of a cow or a chicken. You just need to ask: Am I treating this being as a resource? If yes, and you don’t have to, then stop. That is both actionable and measurable