Yes, it is national interest. "Saving lives" IS thebusinessresponsibility of government. The costs of not being forewarned are too devastating in both long and short term.
Weather forecasting is crucial still when the navy/air force are needed.
Can different agencies be combined, responsibilities and costs pared? Without a doubt. I've never been convinced that the Federal government has any good purpose in education, it should be at a local level. In any case, the government will always expand without pressure to reverse or at least slow down.
However, it shouldn't be done willy nilly by proclamation of people who really don't know the nitty gritty of what is done. Some, even most of what an agency is charged with, may be non-essential, but there may be some that are crucial.