Why not do what you can do to affect positive change, live a fulfilling life...
Philosophy (aka intellectual masturbation) is itself fulfilling and stimulating for a lot of people even if it doesn't translate to amazing new truths, answered questions, or applicability to real life (and it sometimes does). Think of the last time you or someone you know spent an hour in front of the TV and compare it to a person who spent an hour debating metaphysics. It is probable that neither one changed anything or made anything significant happen as a result of that hour. But the intellectual probably had at least a good a time as the guy with the boob tube.
Beyond that, there are some questions that everyone answers individually - "How should I live my life?" "What are my values?" etc. will always be the subjects of debate because no one has come up with an irrefutable answer yet coming to individual conclusions (or partial ones at least) on these issues makes a person's life more fulfilling and purposeful. For religious types, metaphysics and theology fall under this category as well, because if you believe in a god, the nature of that god has a direct bearing on how you should behave and what your more specific beliefs should be. From an atheistic standpoint, I don't feel the need to actually worry about metaphysics because I'm already leaning well toward the "nothing I learn about the universe will matter" camp (I don't really *worry* about anything), but there's always a chance I might discover something important.
I posted this, like just about everything I post in philosophy, because it is a more satisfying use of my time than a lot of other things I could be doing instead (like posting in other forums), *and* it could lead me to some new insight, which is what differentiates discussion of the existential, the incomprehensible, and the metaphysical from discussion of the temporal and the mundane. Whether or not it leads me to a revelation, it feels good now. Intellectual masturbation, indeed.