I get that “The Purge’s” premise had a lot more potential then the movie itself, but the fact that it’s billed as a “Speculative Thriller” should illustrate what sort of aim it was really going for. It’s not so much about what people will do during The Purge as it is why it exists and whether or not violence is something we truly all need to “let out.” By the end of the film I think it’s abundantly clear that the real “Purge” going on is of the underclass of society.

The fact that it doesn’t focus on the myriad of violent acts including sexual assault shows that the film doesn’t want to be a perfect analogue for our own world, which is vastly overused nowadays anyway.
Ultimately I think this makes it film that really isn’t about anything except the idea at the center, which means the story and characters are largely inconsequential. It made enough to merit a sequel however, and maybe then we’ll get a larger scope of the world and the other ways people react to The Purge…