In my mind there is never a doubt as to weather a buyer or for that matter a seller should have a home warranty policy in place. It is the norm here in California for a seller to pay for a home warranty policy for the buyer.
But... what about a policy for the seller? It is not the norm to have a seller get a policy on their home when the listing is taken and many agents are not aware that seller's coverage can be purchased during the listing period. Seller's coverage runs around $1.00 per day and is paid at the close of escrow if the house sells or if the policy is actually used and the seler does not move forward with a sale.
As we know in this business, expect the unexpected. It's like Murphey's Law, if it can go wrong it will go wrong and at roughly $1.00 per day if it does go wrong, isn't a $60 service call for a plumbing leak much easier to swallow than a bill for $625 because a plumber had to go out on a Sunday evening?