You're correct, it isn't. Planets in very close orbits tend to be tidally locked. Instead the significance of the moon is thought to be as a stabilizer for the

You're correct, it isn't. Planets in very close orbits tend to be tidally locked. Instead the significance of the moon is thought to be as a stabilizer for the Earth's rotational axis. However, our axis is not exactly as ultra stable as some people think - it's still shifting up to a few degrees every few million years. It's also worth noting that six out of nine planets in this system are oriented in the same way as Earth and none of them has the same moon configuration as us. For example, Mars has pretty much the same tilt as us and its moons are pitiful. I personally don't believe it's a requirement for life. We simply lack the empirical data needed to make any assumptions about habitability or even the basic configuration of habitable star systems. Until then, looking towards twin Earths is probably a good start to look for life but it's certainly not the only kind of environment stable enough to support it.