+1, we don't need a cold storage proof, we just need solid withdrawal proof, a cold storage proof can't prove payment, the best example is that satoshidice has a cold storage proof, but it doesn't pay to some players now.
Many good and reliable casinos don't show them but they pay instantly, no cold storage proof means nothing.
Proof of funds in cold storage shows that the casino actually has the funds to pay the bets they offer you to place. If they decide not to pay that's a different problem.
If I was looking for a place to play I would rather pick a site like PRC, BD, JD etc that shows proof of funds so I know they have the money to pay if I win and not a site like DaDice that doesn't show proof of funds. You cannot guarantee a site like that has the funds to pay you if you do win regardless of withdrawal history.