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.
A game that requires no skill doesn't make one dull either nor does it mean that the brain is not used, the brain is always at work but however not using it to make tactics and think deeper like you do in other games might be the reference point yet it doesn't make you dull because few hours of not making high end thoughts doesn't decide the whole of your life or your brain capacity it's just temporary, for a moment.