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.
Even if you have a great capital, it doesn't guarantee higher chances or a consistent profit of $100 per day. It's always risky to do that especially if done on a daily basis. This is because luck may not always be on your side and at any moment you could lose a big amount of money.
For example, consider having $1000 and attempting to place a bet on odds of 1.1, which would yield a $100 profit. While a 1.1 odd might appear relatively safe repeating this bet multiple times a day could eventually lead to the loss of your initial $1000, so yeah that's what I meant.