Who said these trains run empty? ЁЯШВ I can agree your point on Rajdhani but definitely not on other, you must research, It's a hectic task to buy a ticket to southern India in such trains and you say trains are running empty. Just because you booking tickets in a non peak season that doesn't mean train are running with this occupancy all the time.
I just you booked a ticket for the first time on this route that why you are such vocal to extend these trains further. ЁЯШВ