For financial reasons - to win money, because someone enjoys thinking about what they would do if they won a jackpot, or because winning would change someone’s lifestyle.
Never make this your primary reason why you gamble because if you do this you will end up losing everything and become a chronic gambler, you cannot keep up and you will not be able to turn down the table and you cannot bring down the house, you can win a jackpot from time to time but never at all times, you must accept this truth, have a good time and if you win a jackpot then be happy that you did.