Many things pair well together. Bacon and eggs. Sunshine and reading. JRPGs and urban fantasy. Gaming subgenres often form out of a continued "Eureka" moment where players and developers realize that two distant genres actually work quite well together. Survival games are about struggling to exist against impending threats from the natural world, and horror games are about struggling to exist against impending threats from the unnatural world. Combine them, and you have the survival horror genre, and many instant classics within them.