Science Fiction and Energy Weapons

Several of the science fiction films we have watched including Alien and District 9 include some sort of energy weapons. When I refer to energy weapons, I am referring to any type of weapon that is not of the traditional projectile-releasing type. These types of weapons have caught my attention because they seem to be unnecessary to say the least. The current state of human military innovation has proven time and time again to be perfectly capable of causing as much damage as desired to a target. The question I now find myself wondering is why there is a fascination with such advanced weaponry in science fiction. The weapons found throughout science fiction films are far beyond the realm of the necessary or useful for any sort of task that might appear in the film, yet the weapons still appear very often. It is true that weaponry is one area of technology, just like any other, that a science fiction film would seem to push the boundaries of. My only concern with this subject matter is that it is an inherently dangerous technology that has been focused on. This thought led me to the question of whether or not all science fiction films must have some sort of inherent warning in them? Is this why they always seem to present some sort of danger or troubling technology? Also, would it be possible for there to be a science fiction film that focused on some technology that was safe and possibly beneficial for all humans?