Departments follow the law with regard to hiring. It's helpful to have officers on hand who speak various languages, and if there are residents speaking those languages, and this is often (but not always) reflected by the background of the person. Hispanics aren't the only ones who speak Spanish, so if it's related to a language barrier, any officer who speaks Spanish should suffice. There are certain areas that believe it's important to try to match the demographics of the force with the community. When I lived in Boston, the Boston Police Department was specifically looking to hire gay police officers, in an effort to connect with that community. It's also important to remember that demographics of areas change. If you look at specific sections of cities, states, and countries, the demographics don't usually remain static, and it would be ridiculous to hire and fire certain people, or constantly shuffle people from one area to the other in order to match the specific racial backgrounds in those areas.