niektore perlia:

Because there isn't enough fertilizer and agricultural land in the world for all of us to be vegans/vegetarians and meet our nutritional needs....

Because animals (especially sheep & goats) excel at eating and digesting the scrubby vegetation that covers much of the earth and converting it into usable protein for us.....

Because without humans to shelter them, domestic livestock would live very brief and severe lives....Evolving to dying out completely. (Arguing here for small-scale, grass-fed, affection-laden living situations).

Because livestock enables people/families in marginal situations to create income that contributes to other advantages such as more/better education.

Because veganism, especially, is disrespectful of living systems and earth history.