Because it's not a healthy industry. It's a vice and not a hobby that could make you more productive or focused in things that you do. You could easily get sucked in type of situation that feels like hell where getting out is another miracle.
Indeed because when you get addicted to it it's hard to quit and the more you think you quit the more you get involve.
Gambling portrayed like this is because of the people itself that drives their intuition to play more and eventually get hook and addicted. Everything that leads to us to addiction is label like this because addiction can't do nothing thus can bring us to our worse version.