I don't think it's MAP that's the real hangup. I think most of the retailers don't think they have to take a hit as long as no one else is doing it.
There are two reasons a legit authorized retailer will abide by an MAP agreement. First is that they're more strictly enforced than ever and the penalties for violations are draconian. They include losing co-op dollars, losing reimbursement for rebates, the vendor refusing to ship more of the item for which the MAP was violated, losing authorized retailer status.
Second is we entered into an agreement and violating it would be unethical. We honor our agreements with our vendors just as we do those with our customers.