2 limitation that casinos have right now is that they are only allowed to lure in people over the age of 21, and that it takes time and work to travel to one.
These "games" are trying to put a real-life, genuine casino in the pocket of every man, woman and child and get them hooked. Slot machine and roulette tables are being replaced by imaginary farms and petting zoos.
We also have thousands of years of social antibodies for gambling, but none for FarmVille. Nobody in my family would offer a nephew the opportunity to get into debt to a casino in return for a pink roulette wheel, but the FarmVille analog hasn't been e.g. the focus of Sunday sermons for a lifetime.
