Magstripes are only incrementally harder to reproduce: the equipment is more expensive, but still available to any attacker. That the magstripe is visually opaque contributes to a false sense of security -- people thinking the magstripe info is somehow locked against unauthorized use, even though it's still essentially plaintext.
The magstripe is thus a bit like the 'lock icon gif' on an insecure login page -- creating enough of an illusion of security to assist commerce, but ultimately misleading. A visual barcode would be more honest: letting anyone see/possess your card long enough to scan/photocopy it is the exact same level of risk as letting them swipe it through a magstrip reader.
