I think andrasz has hit the nail on the head. And whether or not Boeing also believes the loss was due to willful human action (as oppposed to any technical malfunction or pilot error, or combination of those) they are unlikely to spend large amounts of their own money to continue searching.
Another view
Similar to the China Air B747 freighter whose search for the critical pieces in the ocean dragged on and off. Some of us felt not enough effort was being expended by governments . In the end we were damn unhappy when the El Al freighter crashed before the China Air one got sorted out. We vowed never again !!!
Now I'm not being critical of the MH370 search to date but there is this knawing feeling that mysteries are not good for the industry and if we have another it will have much larger repercussions.