Unfortunately none of the arguments about what the Chaco great houses were used for is convincing.
First, sure, from the outside, the great houses look like later and Native American apartment but the inside of the great houses casts serious doubt on the idea that many people lived there.
If hundreds of people were living in the great houses, then there would have to be many fireplaces, where each family did its daily cooking, but there are very few fireplaces.
In one of the largest great houses, there were fireplaces for only around ten families.
Yet there were enough rooms in the great house for more than a hundred families, so the primary function of the houses couldn't have been residential.
Second, the idea that the great houses were used to store grain maize ; unsupported by evidence.
It may sound plausible that large empty rooms were used for storage, but excavations of the great houses have not uncovered many traces of maize or maize containers.
If the great houses were used for storage, why isn't there more spilled maize on the floor?
Why aren't there more remains of big containers?
Third, the idea that the great houses were ceremonial centers isn't well supported either.
You know that mound at Pueblo Alto?
It contains lots of other materials besides broken pots, stuff you wouldn't expect from ceremonies.
For example, there are large quantities of building materials, sands, stones, even construction tools.
This suggests that the mound is just a trash heap of construction material, stuff that was thrown away or not used up when a house was being built.
The pots in the pile could be regular trash too, leftover from the meals of the construction workers.
So the Pueblo Alto mound is not good evidence that the great houses were used for special ceremonies.