In Spider-Man 3, there was a whole character named Dr. Wallace (Adrian Lester) who got completely cut. He's the biologist Sandman forces to cure his sick daughter, which is why he was stealing money in the first place
In the deleted scene, Sandman comes out of an air vent in Wallace's lab, confronts him, and slams him against the glass wall demanding a cure.
Without him, Sandman's entire motivation makes a lot less sense in the final film.
Sam Raimi personally called Adrian Lester to apologize for cutting him, the movie was running over 3 hours.