When it comes to withdrawals, casinos have two types of business model:
1. Pay user's withdrawal fees out of their own pocket
2. User pays fixed withdrawal fee
This is also strictly business, some will not request for a withdrawal fee all because they understand the way gamblers will appreciate this as opportunity and be rest assured of using their platform each time as to make withdrawal can never be an issue for them, just as the way they never finds it difficult to make deposit, while in some cases, some will charge below $1 and I've seen those that charged more than $5 to make withdrawal, to me, they are doing this to keep gamblers on the run of using their entire money to gamble, when they consider the cost, it may be discouraging, they may then decided to leave such for playing game instead of going towards the withdrawal fee charges.
All are business strategy to attract customers when a casino isn't taking withdrawals fees, but in all what I really take into account before all else is the reputation of the casino, and then their withdrawal speed. But it's an advantage to the gambler that he gets to use a casino with a free withdrawal fee, in that way you are sure of getting back all your money in one piece. But should a casino charge for withdrawal fees it shouldn't be something high, anything below $0.50 fee charge seems okay for me.