You are right and there is no gambling games that should be considered brainless except the person has another definition of what they meant by brainless if not we have only understand one thing about being brainless and that's what you have already stated, perhaps OP wanted to use another word to describe his motion but ended up using this instead, or he might be thinking that those games that doesn't involves any thinking is a brainless gamble that is why he highlighted those games because in roulettes there is no calculation or any reliable strategy because is almost like spinning to be lucky for it to roll to the number you picked, so actually that's what I think was the reason why OP called it brainless.
I think you got the point of what the op what's trying to say perhaps his expression was misunderstood by some person, how would you want to classify a gambling activity that doesn't require you to think much, all you just have to do is to spin which means your fate is just been decided by luck, in sportsbet atleast we can try to analyze football based on the current form and history of the teams involved and with those we can come up with some conclusions on the selectiona to make although trying to predict with the aforementioned strategies doesn't assure any wining but it put your brain into action to think out something so that you can stand on that to make your selections, the op can also explain further, may be we are overthinking perhaps the op might also be having another thing in mind while making those statements.