Gambling is just like smoking or drinking alcohol. The individual who participates in it may lose his money and health. But at the same time, these activities contribute huge amounts of money to the government coffers.
It gives money to the government through taxes but to the user of those two that you mentioned are mostly losing everything to the user. Unlike in gambling, it may not lose any health related to the gambler. And these beliefs that has been passed for generations believed that gambling was always negative and it will never bring good to the people. That's partly correct but it will only happen if the gambler is really greedy and want to be rich quickly. Everyone has been oriented with the possible result so its portrayed negative all of the time.