Also there are many gamblers who don't care about paying high tx fee because they are even willing to loss thousands of dollar in single play in casinos, so those 20$ in fee might not hurt them.
On some gamblers then yes but most of them will really have on doubt regarding on fees which is too high but same as being mentioned above we can anytime play up by using altcoin which most gambling sites are offering now and by these we can avoid high fees on each transaction either withdrawal or deposits. $20+ fee wont really be nothing into those rich gamblers out there.