For me horror is not just about being scared it is about being disgusted too so gore has to be a part of it. Gore do not scare me unless it has to do with the eyes but it still is an important part of the atmosphere of an horror movie. And also when the rest of the movie is well done and you can identify to the characters in it it makes you think about the real horror that happens to innocent people in life. It even helped me once when I had to have work done on some teeth, I kept thinking about the movie that I watched the night before (Hostel 2) and then started to think about the victims of psychopaths and that was the only time I did not cry, scream and have a panic attack while getting fillings.
If I only want to be scared without being disgusted then I watch a suspense movie.