Why are the largest cities in India on the coastline?

It is not like all the large cities are on coastline. Cities like Delhi, Bangalore, Chandigarh, Jaipur, Bhopal , Lucknow, Hyderabad are not on the coastline . Its true that cities like Mumbai, Kolkata, Chennai, Vishakapatnam are on the coastline.. Its because India is an old country and earlier most of the economic income used to come from the exports by ships. And all of this cities have big ports along the coastline.