With smartphones quickly becoming the most popular gadget in the world right now, which allows people to play Blackjack or slot machines wherever and whenever they want, introducing the Vita to casino titles would make good sense. Sure, there are a few titles that cater to the casino genre such as the Hard Rock Casino game but all of them are merely free-to-play. People don't have the option to play for real money.
The PlayStation Vita is by no means a family-oriented gaming station like the Nintendo Wii. As such, it would make sense if Sony allows developers to release games for the adult demographic. Even DC characters -- comic book icons that were supposed to only appeal to the young people now have slot games made after them. Batman, for example, has a "The Dark Knight Rises" game that not only immortalizes the franchise but also helps promote slot games to fans of Gotham's greatest hero. DC probably agreed to this setup given the fact that they don't only have a huge following in that demographic. They also have hundreds of thousands of adults who follow their comic book superheroes religiously.
In addition to fans that are old enough to play slot games, Sony should expand its entertainment choices in order to stay competitive in the gaming genre. Sony isn't the one dominating the handheld platform now as more and more people are switching to smartphones instead of consoles. When Sony will actually become open to the idea is unknown but should they do so, they have a good chance in boosting their target market considerably.