Primarily crowd control, I've seen them used during the rougher years of football hooliganism when I was younger. They're very effective when in a line, people scatter. It's more of an intimidation thing these days, but it works. Don't mess with working animals that kick and also bite.  But they are under threat too. I'm of the opinion that they're not worth the cost but then I wouldn't be surprised to see more bodies and more dog handlers taking their place.