Why are there so many studies about a non-existent problem ? If you want to model a disease, why not a deadly flu ?
People don't pay attention to scenarios involving plain old flu. Zombies are essentially a placeholder for all types of disasters. Responses to zombie outbreaks include quarantine, crowd control, logistics, evacuations, communication with media and the population, areas blocked off due to a natural disaster(flood, earthquake, etc) modeled as "infected area", etc. For people, a zombie "bug out bag" containing water/food/medicine is good to use if you lose power or have to evacuate to a shelter during storms/disasters, and planning routes to avoid heavily trafficked areas are helpful if given an order to evacuate as well. Zombies are just a generic disaster that cover pretty much every facet of any kind of disaster response.