The reason why Venom was included in that film was because the idiot producers at Sony forced Raimi to include him in it. His original script only had the Sandman and Vulture as the villains. I remember reading about that a long time ago too. But everyone kept asking for Venom and Raimi was forced to alter his whole script. That ended up making Spider-Man 3 a stupid film and was just too much for it to handle. Sandman being Uncle Ben's killer, the symbiote arriving to Earth out of nowhere, Peter going emo, Harry being the new Green Goblin, Brock becomes Venom, and then Harry dies. My head is about to explode. Because of all this crap, Sony had no choice but to reboot the Spider-Man franchise for the sake of keeping it away from Marvel Studios.