Here is some reasoning for funding -- i.e., US Congress funding -- high energy physics (HEP), e.g., the Large Hadron Collider (LHC), I didn't see mentioned here:<p>(1) The Russians, EU, China, Japan might pursue HEP so the US does not want to appear to <i>fall behind</i>. So in part, the funding is "a matter of national pride".<p>(2) The funding has a <i>constituency</i> and keeps it and the university physics departments going. The US does want healthy university physics departments if only to teach physics for all the roles all of physics can play in national security, NASA, the economy, other sciences, e.g., medicine, engineering, e.g., computing, etc.<p>For the power of <i>constituencies</i>, notice that a lot of physics laboratories were started during WWII and are still operating. One way and another, somehow they keep getting funding.<p>(3) In the Manhattan Project the world, the <i>power elite</i>, all of civilization were surprised, shocked, felt blind-sided, afraid. The lesson they took was: It's a big, complicated universe out there; a good guess is that not nearly all of it is well understood (true or not); so we must pursue physics, at least <i>keep up</i> as <i>insurance</i> against another shocking discovery.<p>(4) The US likes to claim to have the best country, economy, culture, human rights, standard of living, roads, bridges, public health, Internet, ..., cars, hamburgers, milk, pizza, etc., basketball, Olympic athletes, pop music, etc., nearly the best of everything, in particular the best universities. So, can't have a great university without at least a good physics department, and very much want a great physics department.<p>Short version: The US wants to be the best, e.g., be the first to put a human with a flag on Mars, the Stars and Stripes.