It is the business model. There is an incentive to make games addictive. Like arcade games the goal is to keep kids as much time on the machine as possible. But now the arcade is in your pocket 24/7.
Even worse, there is an incentive even to just open the app as it is an opportunity to show you an Ad. Notifications, and periodical rewards make sure that there is a constant need to interact with the phone.
Unregulated markets will always end up in scams and addiction. Because both are the fastest and more reliable way of getting money.
