Gambling is haraam because Allah has forbidden it, and He rules as He wills. Allah says (interpretation of the meaning):
“O you who believe! Intoxicants (all kinds of alcoholic drinks), gambling, al-Ansaab [sacrifices for idols, etc.] and al-Azlaam [arrows for seeking luck or decision] are an abomination of Shaytaan’s handiwork. So avoid (strictly all) that (abomination) in order that you may be successful.
Shaytaan wants only to excite enmity and hatred between you with intoxicants (alcoholic drink) and gambling, and hinder you from the remembrance of Allah and from al-salaat (the prayer). So, will you not then abstain?”[al-Maa’idah 5:90-91]
With regard to the wisdom behind this prohibition, any wise person will see that there are many reasons for it, including the following:
Gambling makes a person rely on accidents, luck and wishful thinking for his earnings, instead of hard work, the sweat of his brow and paying respect to the ways prescribed by Allah.
Gambling destroys families and causes the loss of wealth through haraam means. It makes rich families poor and humiliates proud souls.
Gambling results in enmity and hatred among the players, because they are consuming one another’s wealth unlawfully and getting wealth unlawfully.
Gambling turns people away from the remembrance of Allah and from prayer, and pushes the players to have the worst of attitudes and habits.
Gambling is a sinful hobby that wastes time and effort, and makes people get used to laziness and idleness. It stops the ummah from working and producing.
Gambling pushes people to commit crimes because the one who is penniless wants to get hold of money in any way he can, even if he has to steal it or take it by force, or through accepting bribes and cheating.
Gambling causes stress, illness and nervous breakdowns. It breeds hatred and in most cases leads to crime, suicide, insanity and chronic illness.
Gambling pushes the gambler to bad behaviour such as drinking alcohol and taking drugs. The atmosphere in which gambling takes place is dimly lit and filled with cigarette smoke; people talk in hushed voices and whispers, and sneak in and out as if they are up to no good. They come in hesitantly, filled with suspicion, and gather around the green table, breathing uneasily and with their hearts pounding. They are supposed to be friends playing a game, but in reality they are enemies, each of them lying in wait for the other and trying to make gains at the expense of the other and his children. The owner of the place tries to numb the feelings of all participants by offering dreamy music, fallen women, all kinds of drinks and cigarettes. The green table is surrounded with cheating and deception. The waiters and girls may tell one player about another player’s cards, helping one player to beat another by means of nods and whispers. Sometimes they achieve a kind of balance to make sure the game carries on and people stay for longer. No doubt everyone loses in the end, they lose the money they spend on drinks and cigarettes, the money they give to the waiters, the money they spend on drinks for the girls, and all kinds of other losses. Even the one who wins all or most of the games loses all or most of his winnings, and the loser loses everything. And at the end of the night, they all sneak away, showing the signs of depression and humiliation, and the loser warns the winner to look out the next day. (Ahmad Shalabi, al-Hayaat al-Ijtimaa’iyyah fi’l-Tafkeer al-Islami, p. 241)
How many families have become poor because of gambling? How many mouths have gone hungry, how many bodies have become naked or been clothed in nothing but rags? How many marriages have failed, how many jobs have been lost, because of a person who stole money to support his gambling habit? How many men have sold their religion and honour at the gambling table? Gambling destroys everything, even when the aim is money. It includes wine, smoking, bad company, darkness, confusion, cheating, hatred, watching for opportunities to take advantage of others, deception and all other kinds of evil.(Qadaayaa al-Lahw wa’l-Tarfeeh, p. 388)
We ask Allah to keep us safe and sound.
(Source - islam Q and A)