Whether useful to every gambler or useless, he may feel better at gambling if he has maximum concentration, although it will not change the chances of winning from slot games. But maybe it does have a point in concentrating on one thing and not being distracted by another so we can enjoy it. Or maybe some players don't need maximum concentration in gambling because playing slots are based on luck so they don't really need to be serious about playing slot games.
I can't get an idea to be concentrated playing slots. I can understand why people get concentrated playing poker or chess, but can't get it when it comes to dice or slots. You're spending not only your money, but also your free time. lose-lose strategy, as for me.