It's said about brain that, "use it or lose it" — now, question being, do you think if person plays brainless gambling games such as slots, dice for major part of his/her daily routine, will it make him/her dull?
Edit: "brainless" as in playing gambling games that does not require using brain, I thought it was clear especially given examples.
Well, I honestly do not think there is any such thing as brainless games, for even the games you mentioned as an example are not brainless if you ask me, except if reasoning is different between humans and gambler.
I say this because I've never seen myself playing a slot game or any other game you mentioned in your example with absolutely nothing in my brain, I think alot and when ever I am playing games like slot, even though the game itself is one that doesn't put any strain on the brain, I still think about something, either about the game or something else to do with my life so as to better it, I do not how some people can go without them thinking about anything, for I still think even when I am sleeping which often times will look like I am dreaming, but in reality, it's simply just what I have in mind while asleep.
So, in the nutshell, I just want to say that I do not believe there is any such things as brainless games, except when and if the party has some kind of issues with their brain.