What if we do it because it's in our nature to explore? Just pure curiosity? To increase our understanding of existence and evolve into something more? Also, this concept of it's safer to find aliens before they find us sounds like you're already of the mindset of war and you want a tactical advantage over something that you've never seen or know anything about. I really hope not everyone thinks of exploring the universe as just another military mapping of strategic attack/defense positions. If the human race is still being driven by fear and war when star-trek-style travel becomes possible, then maybe it's better we just die right here rather than export our madness throughout the galaxy.