Murphy has artificial value because he's 36th in the NHL in ATOI over the last five seasons amongst NHL Right-Handed Defensemen with at least 200 GP in that time period. Add that he's not ancient or "currently" injured without being too expensive to acquire or from a salary cap perspective. There really just aren't that many options if you need a guy with experience. Not necessarily talking moving from 18th -> 10th which is a lot, but just that there's "something".
Adam Larsson is probably the guy people are calling about, but if Seattle just says no, your team is on his 10-team no trade list or it becomes an expensive mini-bidding war, maybe you kick the tires on Murphy.