Sooner or later, they will addicted to gambling. Once that is happen, they will ruin everything they have and even their life.
Each gambling addicted is different. Being gambling addicted isnt something uncurbable and does not mean that everyone will ruin their lives with 100% probability. I think everyone who has tried gambling at least several times are already addicted, because they return to gambling anyway. We have different forms of addiction, someone return and gamble daily, someone on special occasions, someone gamble once each month. But that does not mean we all are moving towards ruining lives.
I won't call returning to gamble part of addiction, we always want to return back to anything that keeps us entertained. Addiction is about unnecessary and uncontrollable act of gambling, it has to always give painful repercussions. If i gamble everyday without being untouched with how much i spend on it, i am not an addict where as i begin using funds meant to care for my expenses or taking deep risk just for profits sake then that is addiction.
But you are addicted, if you have gambled yesterday and return today. However this is a light or harmless form of addiction. Call hobby or passion as an addiction as well. I call an addiction a process, an activity you want to repeat again and you repeat it. «Unnecessary and uncontrollable act of gambling» I would name as reckless gambling instead.