They share a lot. They are addictive, and the further in you get sucked, the harder it is to stop. Because of this, the further in you get, the easier it is to be exploited and taken advantage of.

I don't think it's about being puritan, it's about protecting the most vulnerable members of society from themselves.

For example, say you get 95% of the way through a game, then the game asks for $100 to get past an absolutely impossible stage, they'd probably get a fantastic amount of people spending the $100 reluctantly. Which IMHO isn't a nice way to do things.