The Guest : The Parents (spoilers)

I like how the parents, especially the father, tried coming off as such authority figures like they knew what was best and were adamant about their dumb choices and ended up being so wrong. The mom was complete aloof to the point that when she got stabbed I didn't feel that bad, she kind of had it coming.

If David is supposed to be escaping, it seemed pretty lame and bloodthirsty of him to crash his car into Spencer's car head on, shoot him, then run off on foot. WHY??

What are they doing? Why do they come here?
Some kind of instinct, memory, what they used to do.