We must confirm the identity of every player who registers for the sportsbook to ensure that all players are at least 21 years of age and are not self-excluded from gambling in any capacity. 

Online sports betting sites are subject to the same money laundering laws as banks are in the United States, and have to make sure to have a record of every player's name, address, and Social Security number in the event of questionable money laundering tactics. It's not only for the protection of the online sportsbook, but it's for your protection as well.