Continuity mistake: When the Vulture gets into the damage control truck he grabs some items from there and puts them in a bag. He didn't have the bag before he jumped in.
Continuity mistake: When Peter breaks the door of the damage control truck, the black bag behind him disappears and reappears between shots.
Continuity mistake: While Peter is doing crunches with Ned his hands change positions between shots.
Continuity mistake: When Peter steals Flash's (Dad's) car and hits the bikes that were on the side of the road, there is no damage on the front of the car in the next shot.
Continuity mistake: At the beginning while the Vulture is talking with the damage control people, he has a piece of paper in his left hand which is folded and unfolded between shots, and which also changes hands.
Continuity mistake: At the Washington Monument, while the officer is helping the kids to come out of the elevator, she disappears when Flash exits.
Continuity mistake: When Peter gets to his home, he is crawling on the roof and shots some web on the side of the door to close it, in later shots the web disappears.
Continuity mistake: At the beginning while Michael Keaton is working with the debris, an extra is going towards him but in the next shot has disappeared.
Continuity mistake: Before Peter leaves the grocery store he gets a plastic bag for the candies, in his left hand. It then switches to his right between shots, and then when he is outside the bag disappears entirely.
Continuity mistake: While Liz and the others are having fun in the pool, one of them in the background disappears between shots.
Answer: Several reasons, the Vulture isn't really a super villain, but a man trying to provide for his family after being cheated by the government. He also can make Peter Parker squirm with fear knowing that he's Spider-Man. What will he do with that knowledge.