If they watch too much television, they may think you will just wave it in their direction to scare them away.

In the real world, many of us understand that a firearm is not a magic wand to be waved but a tool to be used.  

If I point a loaded firearm at you, that is because I intend to use it so that you cannot continue committing the crime of burglary in a dwelling or one of the other justifications for its use.  The best way to do that with my skill level is aiming for your center of mass.  This may possibly kill you and certainly is likely to incapacitate you.  

You chose to risk that outcome when you entered my dwelling or committed one of those other crimes.