I noticed that children do not tend to gamble in countries with decent laws. So if you have gambling available for children at every corner shop, then maybe it is time to reflect on your countries laws and those who make them.
Any habit/addiction-forming substance or activity will stunt the development of their young brains. Gambling should not be accessible to children, just like alcohol.
If there are no laws, then the store owner should, at the very least, be the responsible one and not let children play the machine.
It is not about the lack of laws, though. Laws can be there and there can be a legal base for people who allow children to have access to gambling to be prosecuted, but the actual problem is corruption and how people in position of power bend those rules and regulations in order to fill their own pockets.
In the case of developing countries, I can give my own experience. Here in my country gambling is strictly regulatef can be only be operated by people with a license, in spite of that there are people from Chinese descent who keep their small mini casinos hidden from the public and which are operated with little to no regulation, because they have connections with the local government, which is corrupt.
The dame can happen with the easy access to slots machines for children, those will continue to be in place thanks to someone who is corrupted and is probably getting a slice of the money gambled away by teens and children.
It is unfortunate, but it is how it works, at least here in LatinAmerica.