It seems to me that most casino visitors are rational and play primarily for the sake of adrenaline and entertainment, and not for the sake of earning. We think that there are many "sick" on theme of gambling only because their terrible examples are very vivid and cause a strong emotional reaction.
This happens because their stories are what everyone remembers, no one notices the person that gambles responsibly and losses an amount of money they can afford to lose, but you cannot help but notice the person that has lost everything to gambling because they are very vocal about it and they begin to blame everyone except themselves, this is why in many countries there are very strict regulations to the gambling industry even if the majority of the people can gamble responsibly.