Well, there are many factors at play here. First is religion. All religion supports eating meat, and you know religion is a very strong factor in shaping societal norms. Secondly is culture. We've had meat eating cultures for thousands of years, you don't expect that to change automatically in a 20 odd years of animal rights activism. Thirdly is the fact that the animals can't speak for themselves. This makes them the 'perfect victims' because they can't defend themselves or record incidences of abuse. It's almost akin to a victimless crime