What's the purpose of the Scream Movies?

I don't want to rant of how Scream movies sucks. Don't get me wrong, they're alright, but what's the purpose of it? All the victims are part of the games in each series, and the killer just wants to be famous, and on and on and on.... There must be someone who is the root/source of all these games that's hosting the killings over the years while Becky(main character) is always the one that survives. I just don't get it. How can each villain be a different enemy, do they just want to do it for the hell of it, or does someone want to make a deal for them, like being famous or some sort? I'm asking, "is there any side villain that should also be important?"