call me cynical, but in my view humans rarely do anything for strictly moral reasons, at least not at scale. laws and customs are motivated much more by pragmatism (hard to have a flourishing society with frequent random killings) or at least reciprocity (I'll agree not to do X to you or people you care about as long as you agree to the same for me). modern democracy is an efficient system of control; it doles out enfranchisement just fast enough to prevent violent revolt.

bit of a tangent, but I think this explains a lot of why we don't see much progress with animal rights. exploiting them is pragmatic, and we can't negotiate with them. even if we could, what concessions could they offer? for the minority who currently care, the only viable strategy I see is to make veganism "cool" and to make it easier to join the club (ie, not demand total abstinence).