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?
There is a huge chance that if you focus on playing these types of games, then your primary aim in gambling would be for profit. Implications? You can easily get addicted into this venture; you would also chase that feeling of high every win; and it would be difficult for you to stop.
Playing slots for a long time without a break disrupts the brains dopamine and other chemical balances.
The brain is an organ that develops and produces. If time is spent on things that don't challenge the mind, it can make it dull.
Constantly watching slots can be hypnotizing.
Just to add to what you have mentioned, there is really no merit in playing slots given the risks associated with it. As we all know, this is the game that has the lowest chance of garnering you a win- it really implies that you are chasing for profit instead of entertainment.