As I know it is a bit hard to get a gambling application into PlayStore. There are some requirements to be met before a gambling application can be accepted and listed on PlayStore.
It is also only allowed for few countries so I do not think it is worth the verification process. One other important thing is that the casino should have a valid license as well.
If players are worrying about security, simply play the game on mobile browser. IMO the number of gambler who use browser is much more higher than who are willing to use an app.