In India, East flowing rivers generally travel its long journey through open flat areas which contains huge amount of soil. Due to their flow they cut their bank and brings large amount of sediment with them.
Indian East Flowing rivers generally fall in Bay of Bengal which is a shallow region and they deposit huge sediment near this meeting point which forms delta.
For example: Sunderban is the largest delta formed by Ganga river.
While West flowing rivers generally originate from Western Ghat Mountains and fall into Arabian Sea. Their journey involves mostly mountainous valley rocky areas and contains low amount of sediment.
Their Arabian sea meeting point is partly enclosed coastal body. Due to this they make Estuary instead of Delta.