Time is real and would exist whether life on Earth existed or not, since change has been around since the Universe began. If the Universe has always existed, then so has change and therefore, time.
Why life exists could just be that life is inevitable given the proper mix of organic molecules, warm enough temperatures, energy and time. Life has more than likely taken hold on planets and/or moons of other stars, just as it has here. There are so many planets being discovered beyond our star system, that they are the norm, rather than the exception. I feel that life, too, will be found to be common, as well. As for intelligence, one could question whether the average of all human's minds would be considered "intelligent" on an advanced, more civilized alien's wisdom scale.
Life is a happy consequence or accident. Time is just how change is measured. For planets to form without life around newly ignited stars will require time/change, whether life is ever there or not, for motion and orbits and gravity to do their evolving work.
And yes, if a tree falls in the woods, and no one is there to hear it, it does, still make a sound. Nature does NOT need humans to exist and change, period.