Yes, although they are relatively simple compared to other organisms, viruses are still extremely complex when compared to the simple organic compounds you'd expect to form spontaneously in a pre-biotic world.
That is what makes all the difference. It's an enormous leap to go from a couple of amino acids to something able to survive and evolve and compete against other complex organisms.
It is possible, I suppose, that remnants of other "starts" could have survived somewhere that's totally inhospitable to ours. Or perhaps, so different that they're not even food.
Discovering them would be very difficult, though. I mean, we have a hard enough time with all those "unculturable" bacteria. We only know them now through DNA technology.
That is what makes all the difference. It's an enormous leap to go from a couple of amino acids to something able to survive and evolve and compete against other complex organisms.