I am an assistant teacher at a preschool, babysit for preschoolers, and live with a preschooler, so its fair to say that I know the demographic fairly well. In my observations of them, imaginative play is quite obviously the thing that fills their time the most. Many children re-present things that they more-or-less already know in their game story: playing the role of a mommy or daddy, a pet, or a baby. They go shopping or to a restaurant. Even in costume, say a child has dressed up in a fancy dress and is calling themselves “Cinderella”, they do not necessarily stay in character for the full amount of time they are in costume, they do what their understanding of being a princess is. But when playing with a toy gun or toy sword, the entire time they have the gun they are a shooter.
It may be because there is an undisputed action associated with guns that is also prevalent in a sport or physical activity like tag. I can’t imagine that kids (at least the overwhelming majority) have any understanding of true violence, but rather they are attracted to the fact that something that they do causes an immediate visual consequence. They like the abruptness of going “pewpewpew!” and having a second child “pewpew” back or start crying. They can see immediately that “I did A and B happened because of it”. The game breaks cause and effect up in easily measurable terms. A game of Cinderella or Kitty is much more complicated and effected by many outside sources. There are no easily predicted outcomes in playing Mommy and Baby- there are many variables. In shooting there is running and shooting, I shoot and you are shot, I win and you lose. Also there is the clearly defined goal of being the “shooter”, and the person who is being shot at is only waiting for their turn to shoot.
I’m unsure of exactly of the types of media exposure each child has, but ive noticed that the kids who do play shooting are not exclusively interested in only playing shooting games, they’ll play most other types of pretend games as well. But there are kids who never take part in shooting games. I cant imagine that these kids (ages 3-5), have seen anything gruesomly violent, but probably have seen superhero shows and ninja turtles and angry birds. Guns at this age atleast have no real association to the object in the world, but would not be a game unless the child has seen some representation in their culture of shooting people. Its a different manifestation of a sports activity. That being said, I still immediately stop each kid in my class from playing shooting with a very stern “no shooting/fighting in school play something else” which might only make it more appealing to play because they have to be more subtle about it.