“With all of the problems here on Earth, it is amazing that we can spend so many public dollars on stuff like this. WHO THE HECK CARES?????”
Well, I do for one. But to answer your question more generally, many folks appreciate science in the abstract, as it represents the most tangible search for objective truth we have. It is without a doubt one of the most worthwhile human pursuits, and has had the nice side benefit of improving our technologies in a myriad ways.
Yes, even this type of research potentially has practical applications - dark energy and dark matter are completely new physics.