Why The Hell Are There So Many Horror Sequels?

When a horror film does very well, its only natural to continue the saga to create more scares and gore, however, when does this start to become a problem? Centered mostly around the slasher genre and late 80's to mid 90's horror has become a lot of things and franchises happen to be one of them. As always, we would love to know your thoughts and please listen in as we kill the same teenage camp counselors, just different ways with why the hell are there so many horror sequels.