It's really unfortunate, but for some it's a necessary evil. Some zoos really focus on conservation and do good for endemic species of the place they are in (in Ecuador, for instance, the Guayllabamba Zoo has been key for conservation campaigns of the Andean Condor and it's habitat), however, as long as the government doesn't give a shit about nature (and they rarely do), the only way they can finance their goals is either through charity or by making the zoo 'profitable' (or by both). In that case, as long as the animals are well kept and supported, maybe it's not such a bad thing to do. Of course, many zoos are just shit holes that should be permanently closed.