Finding life elsewhere would end our cosmic isolation: if there is life in our own planetary backyard, then life is probably common throughout the universe. These enticing possibilities are why my colleagues and I have spent 17 years developing a spacecraft mission dedicated to understanding Europa.
Unless Earth is special beyond reason, you can confidently assume there are plenty of societies out there. That doesn't mean that they'll come to Earth (or, as many believe, already have). Interstellar travel, despite what you've seen at the local multiplex, is hard. But we could easily get in touch via radio signals or flashing laser lights.