Most big spenders are incredibly wealthy, like buy $30,000 wristwatches for fun wealthy. Games have figured out how to 'go infinite' on their spend possibilities and capture wristwatch money from these folks.
The other thing novel to games is social aspects. Just like buying fashion to wear in public, games let you show off your money in a way other mediums don't. Music has a near equivalent with VIP passes and private shows, but scaling these are human-bound in space or time respectively, which games aren't limited by.
Second, games provide a sense of community. A lot of game revenue is monetizing people's desire to not be alone. Calling these players addicted is I think reductive. Are people addicted to church? To golf? To therapy? Maybe some of them, but it's a poor generalization.