Why is there gravity?

[Smaug]

So gravity is awesome. It keeps my ass in my chair and my beer in the bottle (provided I hold it right side up). But why is it there? What causes it? Just things having mass? I've searched it up and all I got were ambiguous "We don't know"'s or "That's just how the universe works"'s.
Does anyone else know more on this subject? Is there even anyone studying this stuff?

Seriously, this is one of the most fundamental questions in science. The same thing as with the nature of electric charge. We know to some extent the mechanisms of gravitation but not why it is there. Basically, just asking "why is it there?" is not unlike asking "is there God?" or "what is truth?". No one knows and may be no one will ever know. The question is too vague. Science does not answer "final" or "eternal" questions like that (it's what Philosophy tries to do), it creates models that describe the world more and more precise with each step, each new theory. To say it metaphorically, science tries to asymptotically approach reality.