It is not strange. Our Constitution makers were aware of the concept of federalism. But, intentionally, they did not talk about it. This was because our democracy was passing through a nascent stage where they had to take steps to consolidate different free princely states. If they had been given more autonomy, we might have faced many divisions of our country. They supposed that with maturity of democracy, proper changes will be brought in the Constitution to make the nation more federal. So they left this issue to the people and future leaders to decide about.