I guess with what Jon did, it's sort of like actual casinos. In Las Vegas, you can make a lot of money doing this sort of thing with promotional offers and funbooks.
The idea is, they lure you in the casino and give you a reason to try out the games, in hopes that you will then start playing with your own money. Although they know that there are people like me (and other Las Vegas Advisor readers) that will mooch off them and go from casino to casino doing the same thing, the majority of people will throw hundreds (or thousands) of dollars at the casino they happen to be at, so it works out in their interests to do it.