Eager to know, would be appreciated if someone share his idea.
thanks!
Gambling websites usually mix inputs which means that your deposit address will be used to pay someone else's withdrawal - and when the coin is spent with an address that is known to be owned by a gambling site, that address is also labelled as belonging to whatever site it may be.
This is essentially how coinbase knows that you're sending to a gambling site, probably through the help of services such as walletexplorer.
They are known to freeze accounts that have connections to gambling, so if you are a gambler don't use them.