When I first started looking into Complexity Theory, as an offshoot of my interest in General Systems Thinking, the "practical" benefit was nil.  Nobody was going to pay me one nickel per decade for the knowledge.  Now (30 years later) Complexity Theory is vital for a project I'm working on; a project that has a distinct change of making me a rather nice sum.  

Other knowledge I've acquired over the years hasn't made me a dime and most likely will never will.  

Acquiring knowledge for "it's own sake" gives the learner the same skill set as those who only acquire the knowledge to get a degree as a credential to get a job.  But, in my experience, those who take joy in learning will go on and continue to learn.  Those who only wanted to get a job will stagnate.  The economic benefit, which I do not deny, of continual learning is an ever-expanding skill set that, among other things, allows a person to recognize opportunities and take advantage of them as they arise.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre