A democratic country needs a Constitution because a Constitution serves several purposes. Countries have their own constitutions because it's a need of a country. They are democratic and
that's the reason they have constitution. In democracy, the government is of
the people, by the people and for the people, therefore to protect the
interest of people, the powers of central and state govt. is limited by
the supremacy of the rigid constitution of India, which is also a
feature of federalism.