In my brief career in Theoretical Physics (Okay,what I am doing is more of Computational than purely Theoretical - but that doesn't change what I am going to talk about) I have to face this question again and again. Would it improve the quality of life? Does it have any industrial application? And when they don't get an affirmative answer to any of these - then comes the clincher - why do you do it then?
Tough question. Someday the things we do might lead to something beneficial for the general public. And a lot of times it does. Those monster particle smashers lead to medical use of much smaller accelerators. But that's not the reason we do it. Proving or disproving the existence of Higgs is not the thing people talk about with their morning coffee. And an overwhelming majority of people's life wont slightly be affected if Standard Model or String Theory stands the test of time. Neither they care about where are all the Dark Matter is. So why do we do it then?
As Feynman says "Theoretical Physics is a human endeavor, one of the higher developments of human beings" - we do it because we want to do it. To find out how things really work at the deepest level gives an overwhelming sense of satisfaction. But wait - how many of us would go that far? Few breakthroughs stand the test of time -and most of us would be spending our lifetimes without doing anything fundamental. That raises another question - is it worth it? I guess it is. Just being part of this endeavour is a great feeling - in any field few go on to make the headlines-it cant be any different here. Even when you have not discovered it - knowing that you are among the select people on the planet who can actually understand it (What they call Popular Science is mostly crap - will talk about it in another post later) gives us that wonderful feeling. And that's our biggest reward. We don't do it for the people - we do it for ourselves!