There is no structure within which political and security responsibilities and cost are discussed, let alone shared. And while there are no active immediate threats to security in the Pacific basin, there are significant realities of the sort that classically lead to conflict and war. There are both resource rich states and those that are poor and ambitious. There are burgeoing populations and countries which are mostly empty space. There's every form of government from democracy to dictatorship.
Military equipment is widespread, significant and increasing.
And the historical policeman, the USN, can no longer maintain world wide oceanic control in the face of local opposition. In every country, investments in military capability are occurring despite evident need to spend those monies on other national priorities. The maritime security issues have a familiar ring. Every time somebody buys a submarine all the other maritime trading nations worry. What submarines do best is sink other peoples' ships either by torpedo or mine and they are hard to identify and harder to catch and kill.