The books are so paranoid about getting charged back, many require info to prove that it's not fraud should a player charge back on them. Gives them a leg to stand on when the bank comes saying "hey, this guy didnt make this transaction"
If they have your id etc then it proves that it's not fraud.
5Dimes is one of the oldest sportsbooks on the net. I understand your skepticism, but rest assured they are very solid. Never had even one complaint about them since 2001.
On a sidenote,
Sportsbook.com doesnt require it up front, but may when it comes time to withdrawal.