Anyone that gambles responsibly doesn't have anything to worry about because he is in control of his actions unlike the gambler that's obsessed and addicted. When it gets to that point where a gambler has to take loans to gamble it's obvious that it has become a dependency issue, sometimes gamblers who do this don't care if they win or lose they only care about satisfying the urge to gamble, it's like a drug to them. Gambling has existed for a long time and it isn't a threat to you unless you let it, responsible gambling is the only solution to this.
Gambling is like a double edge sword and it's consequences depends on how gambler handles this sword. It's meant for entertainment but many lose lots of money by getting addicted to it. If one can keep his emotions under control while gambling then he won't lose much in gambling. You are right that it's there for centuries but not every gambler is bankrupt rather the one who got themselves addicted to it. Taking loans for gambling is the worst thing a person can do and if a person has gone too far in gambling then its very much sure that he has lost control over his emotions.