Anonymity: Bitcoin transactions are anonymous, which means you can bet on sports without revealing your identity.
Anonymous in a way that you're not using your first name while betting but that's just the first because if ever you got lucky and got some handful of coins with you after the activity, they will start and establish a KYC (which is by the way common in bitcoin sportsbooks nowadays) before you can actually withdraw your funds.
And why would they reveal my identity? They for sure know that it is against the law.
Security: Bitcoin is a secure and reliable form of payment, which means you can trust Bitcoin sportsbooks with your money.
Sportsbook is definitely not a wallet where it is really secure, therefore security is always an issue.