Horror has a reputation for steep second weekend drops, and it mostly earns it. The fanbase shows up opening night, so the weekend is front-loaded, and then the drop looks alarming even when the run is healthy.
I care more about the films that break the pattern. The ones with gentler drops tend to be the ones people recommend to non-horror friends. Word of mouth turns a genre audience into a general one, and that is where the long nights and slow money live.