|The Shifty Mongoose|
I have the assumption that a small percentage of elementals willingly allow themselves to be summoned, or sign up for it or something. Either they don't really "get" the Material Plane and figure, "It's all fun, nobody really dies. See, I just get sent back home no matter what happens!"
Or they do it because they believe in their evil lords' propaganda of beating up Material people for funsies.
...Perhaps some of them rationalize that, if they were brought to this icky universe and told to smack that guy, it must have been for a good reason, right?
Or, in the case of called/bound elementals, they're probably really bored and willing to take it out on random passersby, just for something to do or the hope they get Dismissal'd back home.