Why Narmada and tapi do not …

The reason behind the formation of deltas in the east coast lies in how the peninsular plateau is shaped. The plateau slopes steeply towards the west coast and has a gentle slope towards the eastern side. This results into:
short swift streams towards the west coast - due to short course these carry less sediment load and thus do not form deltas. (narmada and tapi are exceptions as they flow in rift valleys )
the east flowing rivers cover large distances and deposit their sediments at the coast forming deltas - eg Krishna-Godavari delta, Kaveri delta,etc.
With regards to Himalayan rivers, they form large extensive deltas irrespective of whether they flow east or west - Ganga-brahamputra delata in east coast and the Indus river delta in the west coast. These rivers have long courses, flow through soft sedimentary plains thus carrying large amounts of sediments forming massive deltas dwarfing those formed by the peninsular rivers.