Your analogy starts to break down somewhere around point 3 or 4. It's not that few people use a lock on their locker. A closer analogy would be that the gym installed an electronic lock on each locker, but didn't actually make sure they worked.
It also wildly disconnects around point 6. You make it sound like he stole everything that the users had in the accounts. In reality, he just copied their info. He didn't give himself anything from their accounts, like transferring credits to give himself free cable or something like that. Instead of stealing everything and selling it on eBay, it was more like him going through people's lockers, taking a picture of what they have inside, and then selling the pictures.
It also wildly disconnects around point 6. You make it sound like he stole everything that the users had in the accounts. In reality, he just copied their info. He didn't give himself anything from their accounts, like transferring credits to give himself free cable or something like that. Instead of stealing everything and selling it on eBay, it was more like him going through people's lockers, taking a picture of what they have inside, and then selling the pictures.