I think earth moon system will be quite rare.I think the occurrence of little planets with huge moons may be much more common that we could think at first sight. Only in our solar system we have Earth/Moon and Pluto/Charon, and for what we are starting to know about the genesis of solar systems the collisions between planets and protoplanets in the beginning of this process could be quite common.
Also, the claim that a big moon could be necessary for the evolution of sentient life seems to me too anthropocentric to be seriously considered.
We have also discovered many gas giants in the Goldilock zone of their stars that could have habitable moons.
So, the places in which complex lifeforms can evolve could be very common in our galaxy.
But the occurrence of sentient life cannot be evaluated in those terms.
In fact, the origin of life is a chemical process, deterministic for its nature, while the evolution is an historical process that happens in a completely random way, resulting from the interaction between genetic variabilty and environmental variables, so we cannot use statistic instruments to estimate if the arise of a sentient species may be common or rare.
Moreover, is also impossible to predict the possibility that a sentient species not living in an aquatic environment could develop a technological civilization,
The bulk of the Earth/mars collision that made ours will result in no world at all.
Not saying they won't exist just saying they will be maybe 1 in a million sort of event and most of the 1 in a million the moon will be to big or to small.
Getting rid of all the stars in our galaxy that live in supernova country as potentials we might be left with just the whispy arms of the galaxy that long term life can exist
Maybe a few billion stars that 95+% are not correct star type or quiet flare type.
Alone might be an understatement.
Life Probably in as many places as it can be, but just basic life.