Just watched this, My take

"Why do people never say, comedy for the sake of comedy, gratuitous smiling, or love interest for the sake of love interest."

They do, they just call it something else, for example the equivalent of gore for the sack of gore's in comedy would just be called unnecessarily crude/dirty humor, meaning it lacked the subtlety. Same thing for love interest, they will say unnecessary love scenes that added nothing of value to the story.

Same idea just expressed differently.

Personally I have no real problem with depictions of Sex or violence in a film unless I think it does not add anything of value to the story. a general rule of thumb is, often it is better to let the audiences' imagination do the work for the film, it is often far more effective because the imagination is often more terrifying then the reality. This is why one of the best and most effective depictions of violence in film history is the chainsaw scene in Scarface. In that film there is no actual gore; there is some blood splatter and screaming combined with the sound of the chainsaw plus Al Pacino's performance. That scene would have been far worse of if they tried to show the actual arm being chopped off.

"Interestingly I never heard of this movie until today. edit; the trailer really gives it all away."

Agreed, trailers in general today give way too much away. But this movie had nothing left to add after the trailer. I was genuinely bored while watching it. No real suspense

Often times in your traditional horror/slasher films the lack of motivation from the 'monster' is supposed to add to the terror of the thing. I particularly don't like it because I agree a character we have no motivation to sympathize with I find the characters not very compelling. But since that is the way it is by design, we have to acknowledge it is a solid screenplay for what it was trying to deliver even if it was not to our preference.