Yes security and privacy could be another issue.
If you own 10,000 BTC, you most likely don't want to login with your personal IP to a site which might later try and track you down.
So many large whales probably gamble in smaller amounts and they use VPNs for protection.
For online online wallets most of the wallet providers not accepting a VPN authorization while they are connecting to log into the their bitcoin wallet. Whles will be using desktop wallet or hardware wallet to keep their bitcoin sage. If you are more security concerned you have to keep your wallet.day file
I am pretty sure no whale out there keeps 10000 BTC in an online wallet like Blockchain.info or XAPO.
What I meant is that for security reasons (unless its a site like PrimeDice) many whales most likely use a VPN on the gambling site. They send from their own IP address on Bitcoin Core and it gets relayed, and the site doesn't know which IP sent the funds but it doesn't matter.
When he is on the site, he uses VPN not to reveal his identity to prevent any kind of theft.