India became a Union of States because it consisted of both British-ruled territories as well as many princely states- Some sub-political units of India have a special status.
(i) French and Portuguese-ruled territories were given the status of Union territory.
(ii) Jammu & Kashmir joined India on a special condition.
(iii) Some units were too small to become independent states. They were made Union Territories.
(iv) States in the north-east have been given a special status as they have a large tribal population with a distinct history and culture.