Which best explains why archaeologists and historians do not have extensive information about the Indus valley civilization

Indus Valley Civilization:

As the people who lived in those areas did not built any structure like a monument, temple, or even a palace for the king. Which leaves us with little evidence that they lived in that region.

Explanation:

Little evidence to prove there existence:

There are few evidences which supports the idea that Indus Valley civilization existed in that area. As scientist do not have any structure to analyze and test, which might be built by the people of Indus valley civilization.