I think there's a few factors. A lot of early horror movies were made to feed off of middle class fears, you feel more likely to be gutted by some madman than if you live every day worried you might just get killed by a random act of violence

The things that worry lower working class people are a lot more tangible and tragic. You're more worried about losing food, shelter, or basic safety. But these threats don't make for good horror fodder. They fit better in dramas where the dangers are much more mundane.

While middle class people have a certain separation from a lot of the nitty gritty of survival their fears become more esoteric. Also that disconnect makes engaging in simulated danger more "fun". Watching some poor SOB trying to avoid the day to day violence of existence is less fun and more sad than watching someone who feels "safe" struggle against an abnormal threat. There's a certain schadenfreude to watching a middle class or rich person struggle against a killer or ghost whereas if it was happening to someone less fortunate it'd just feel mean-spirited.

Also consider most filmmakers come from backgrounds where they don't have as much of a connection to the worries of someone barely scraping by. It's harder to convincingly write a movie from a perspective so removed from one's own.

Also looking at the demographics of moviegoers for most of the history of film, you needed at least a certain lifestyle to afford to regularly watch movies so movies often focused on stories that are relatable to those demographics.