if a person gamble just for fun like spending few hours and with 20 dollars a week or monthly, i consider it as a normal, ....
Well that is not normal because we don't have the same financial status.
For people who are making like millions in a month basis, $20 does not anymore give them a thrill and it's just a waste of time.
What is necessary is not the specific amount, it's you gamble what you can afford to lose, and that you'll stay consistent following that.
I am pretty sure that even if a person with a financial status of spending 20 dollars a month or week, they will still play and bet higher than that if they win consecutively. That is how gambling works, you have money, you play in order to make the most out of it. So, it is impossible to just waste that exact certain amount. Sometimes, if we are winning too much and still continue to gamble, all of our funds could be lost, there are instances that it pushes us to borrow money and in that way I can consider gambling as a threat. Mainly, fun with the experience at the start, but a threat to consider in the end.