The story is in the game, you just have to have sharp eyes to see it. There's the bite of '87 which one of the characters bite someone on though it never says why or who and the incident was swept under the rug. A night guard, dressed up as one of the characters, lured some kids back stage and murdered them and hides the bodies in the animtronics. The murder is latter caught but the damage is done. Scott has said that either Phone Guy or Mike has some sort of criminal record and may have even been framed for the murders.
See, this is what I was interested it. Browsing Youtube comments, it was all fan theories trying to flesh out the story, and it was interesting. It's kind of the same appeal as Dark Souls story, just not as mind numbingly inaccessible and convoluted.
Also, by the looks of things, the phone call on night 5 isn't just reversed audio, so there's no clear decodings out there, but I did find one that manages to lift a few half sentences out of it. Depending on your interpretation of some of the words, it could imply the voice is that of a scientist or Freddy himself.
Another thing I noticed was that the security cameras clearly show cobwebs. This led me to speculate that Freddy's is already shut down, but what could that imply? I've seen a few theories, like that you're either the spirit of or the actual security guard who killed the 5 children whose remains animated the automatons. Somehow, they've brought you back here where you relive the same week over and over, listening to your own phone recordings. Golden Freddy is the only suit with no eyes and is never seen moving, always slumped, so it's implied that it's the suit you lured the children with. On night 5, you start to become aware that you shouldn't be here and check the heads in engineering, where you're finally stuffed inside of Golden Freddy, just like your victims were, and after a weekend of sharing their fate, you go right back to the beginning to do it all again.
It's an interesting theory.