Winning a $100 daily from casinos may not be that much and it's kind of quite low to be honest but that's not the whole picture as there will be some instances that you might cross over a $100 in your hands but as expected, you will not call it a day because for the most gamblers, that will not be enough as humans will always want more. And in the end of the day, they will find themselves in a situation where they don't even have a clean $20 profit or worse might've gone overboard than the supposed budget.
If your capital is bigger, then a profit of $100 may be small but if your capital is only a dime because gambling is just for fun then $100 is something very big.
So in this case it depends on capital too when saying big or small profits but when we talk about the context every day, I think it's still something that is difficult to happen and even seems impossible if you want something like this because I still stick to my belief that luck in gambling doesn't come every day and this is what makes me believe that a profit of $100 / day is an impossible thing to happen in gambling.
I think that is the wager is big enough and the multiplier is low, so it would be the risk. I think it is possible for someone to get 100$ daily with a single dice roll.
But we both know that eventually the luck will run out and the bulk of the money being use to get those 100$ will go away in a second.
Besides the size of one's pocket, one can also consider the life style one wants to have or is currently having. For many big whales a constant income of 100$ per day whould not be enough, hence the reason the go bigger with thousands of dollars put at stake in a single session.