A reason for LTA craft to exist is remote accessability. imagine a transport network for developing africa, or outback australia that required no more infratructure than a large open space. the flying boats of the 30's were less aerodynamic, but very popular for being able to land in remote and less developed places. Airships like the Lockheed Martin P791 [
http://en.wikipedia.org/wiki/P-791] don't require ground crew for handling on the ground. it also uses a hybrid 'just lighter than air' vessle with aerodynamic lift from the hull shape at very low speeds.