Continuity mistake: After Peter gets the text from Happy about meeting at the bathroom, Michelle asks, "What are you hiding, Peter?" and just as she says, "I'm just kidding I don't care," Peter's holding his cell phone up in his left hand, but next shot he's holding the cell phone up in his right hand.
Continuity mistake: When Ant-Man goes giant during the airport fight in Civil War, Peter is out in the airfield and reacts with a surprised "holy shit!" His video diary in Homecoming instead shows Peter hiding away from the action, and he reacts to the moment with a more subdued "aw crap, he's big, I gotta go now."
Continuity mistake: When Spidey first interrupts the criminals on the ferry, there are 2 motorbikes behind him on the left. When he throws one of the bad guys around with a web, the bikes have moved to the right, along with the yellow markings they were on, showing the shot's been flipped. They then move back.
Continuity mistake: In Peter's personal vlog of the airport battle from Civil War, he jumps in, grabs Cap's shield and immediately says "hey everyone." However, in Civil War he jumps in and grabs the shield without saying anything, Tony says "nice job, kid", there's a longer chat about the suit, and only later does Spider-Man say "hey everyone."
Continuity mistake: When Spider-Man stops the "Avengers" from robbing the ATM, there's a car parked outside at the start, visible through the window, which disappears a few seconds later, and then reappears after that.
Continuity mistake: When Spidey saves Liz from falling off the Washington Monument, he shoots some web on her hand and wrist which disappears a few shots later.
Continuity mistake: When Spidey falls into the elevator, there is a bag that disappears, reappears, and even moves to the side between shots.
Continuity mistake: When the ferry starts splitting in two, there are people standing at the back and cars on the bottom. In a wide shot the people and cars have disappeared, then the people reappear a few seconds later, as do the cars in a later shot.
Continuity mistake: When Spidey falls into the water he is trapped in the parachute then the armour takes him out and the parachute is gone.
Continuity mistake: When Peter and Ned are removing the tracking device from Peter's suit in the hotel in Washington D.C, Peter has a flashlight in his mouth. He removes it, but in the very next shot, it is back. Later, as he puts it in his mouth, it switches to his hand, and back to his mouth in between shots. (00:47:50)
Continuity mistake: In the ferry fight, in one shot nobody is behind Spider-Man, but in the next shot Vulture and another man are.
Continuity mistake: When Peter Parker leaves homecoming and finds Michael Keaton in the warehouse, at one point the engine is swinging in the crane, the camera cuts away and comes back and the engine is perfectly still.
Continuity mistake: When Spider-Man is at the top of the Washington Monument, in the background we can see a sniper aiming straight at him from the helicopter. We cut to a closer shot of the chopper, and the guy's rifle is suddenly lowered, then he raises it.
Continuity mistake: Near the start of the movie, Peter Parker is doing sit ups assisted by his friend. As the camera moves left, Peter is seen doing the exercise with both hands behind his head but as the camera then moves to a different angle he has both arms crossed over his chest with his hands at his shoulders.
Continuity mistake: Spidey left his backpack attached to a trash bin. Later he gets it back but the alley is different.
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: Spidey took Flash's car and hit a bike, but there is no damage on the car at all.
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.
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.