CSC vs l2vpn

Hi Everybody

While preparing on CSC It happened to hit me, why need this additional complexity of CSC, why not just use l2vpn(ATOm) between the POPs and be done with. Anyway if CSC is used ,the customer external routes needs to be exchanged using mpibgp between the pops, SO why not go with L2vpn even when Carrier Customer uses either bgp or mpls in its cloud. Kindly clarify If I am missing something.

Thanks In Advance For The Replies.