Because Europeans will exchange passive aggressive snide remarks and hallow threats until someone assassinates the archduke of Austria and world war breaks out.
In 1800, that was certainly the case. With mass global media, telecommunications, overnight mail, internet connectivity, and satellite coverage, I no longer think this holds such importance. National matters require a federal government, regional matters require a state government, and local matters require a county/city government. The lines between are not chiseled in granite and flexibility is good. It is not always a virtue to move responsibilities downward, it depends on the matter at hand.
Sweden spends quite a lot on defense for a small country in order to remain neutral. They even make their own jets, ships, subs, helicopters, and tanks. Of course their geography makes Sweden difficult to invade and there is really nothing there to tempt an invader much except steel which they will more than happy to sell you.