The use of animals is a bad idea. Animals have been used and abused by humans enough. Yea I know these are trained and well treated and cared for. But the idea is to NOT promote the use of animals if we can.
Well, in a way, it's sort of an easy way to create a spectacle, isn't it?
The Carmen I mentioned was one of the late Zefferelli extravaganzas at the point when he no longer bothered much to direct the singers in being potent dramatic figures, resorting to generic spectacle displays. I lost track of how many animals appeared in that production but at that point his "technique" was to load the stage with as much "stuff" as possible and let nature take it's course.
To your point, it's far more challenging for someone staging an arts production to concentrate on motivating the (human) performers rather than resorting to the sort of cheesey step of making some poor animal walk across a big, crowded stage with all the lights and noise.
But there really in no end to this. I'm not in NYC all that often any more and don't know if it's still as prevalent as it used to be but my heart always went out to the poor carriage horses walking up 10th avenue in the midst of all the traffic, noise, cabs, and polution. Yeah, they look picturesque in Central Park trotting along , pulling a carriage but unfortunately they also have to maneuver along the regular city streets too . And that's not pleasant for anyone, animal or human.