$20 is nothing for a rich gambler, it was just a throwaway money for them. But for poor people, this is already huge.
There is a post that "I'm rich because I am a gambler". That something defines that rich people can afford to lose money while poor people cannot. But I don't think that if we can afford to lose $20 a day, it's just okay. Certainly, a responsible gambler doesn't see it right.
Although we believe that we could lose more in gambling. It doesn't mean that it was okay to lose every day.
One thing that gambler has to keep in mind is that he will always lose sooner or later. And for gambling 20 USD every day it is decent money when you add it at the end of the month ( 20 USD x 30 days = 600 USD at the end of the month ). I would not waste that kind of money on gambling even if I had money to throw away. I usually gamble much smaller amounts that I will not miss if I lose them completely.