Some ppl gambled for fun that's how their addiction started. If they're gambling with the correct mind it isn't going to become a problem but if their mind gets addicted to gamble it's going to change their life for ever. When you gamble you're going to lose money the companies don't.
Excessive of anything is bad. Gambling is a social vice and a practice that can lead you to addiction. When you fail to realize that you can be addicted for merely gambling for fun, you will limit the time that you are spending on gambling. Healthy gambling should be practiced to avoid bringing shame to yourself and your family members.
Too much of everything is bad including excessive gambling, it can lead to addiction without the gambler knowing how he got to that stage. The best way to gamble is to be in control of your emotions and use small amounts to gamble, if you can do this you won't be addicted. Some people see gambling as a short cut to riches where they will win big after some trials, this mindset is wrong, gambling wins are by luck and you don't know when it can happen or if it will happen. Enjoy yourself in gambling with small amounts and take wins if you're lucky, if not you should move on and try another time.