A clear example how money in the military-industrial complex (or DARPA) directs innovation paths. The military does not approve of hydrogen blimps, and so neither can the civilian sector use them.
The military haven't used airships since the 1930's because transatlantic aeroplanes rendered them obsolete. Not because of some military-industrial complex conspiracy.
Every couple of decades the DoD decides that blimps are back in fashion and throws millions of dollars into blimp projects. Inevitably they cancel the project and decide they don't want them. Admittedly they've all been helium, but the reasons for cancelation are usually related to capability and the intrinsic qualities of lighter-than-air flight, and not cost.
The past 20 years, they tried Integrated Sensor is Structure (USAF) [1]; Long-endurance, Multi-intelligence Vehicle (Army) [2], Blue Devil (USAF) [3], Walrus advanced technology demonstration (DARPA) [4], and a handful of other boondoggles [5].
If anything, the concept of viable airships in the 21st century is just a defence contractor gravy train.
None of the other countries are doing it either, so it isn't just DARPA. I think it just doesn't have an obvious use case.
Everyone says cargo, but what is it better at at than rail, truck, ship, or air (cargo jet)? If you want cheap you go with rail or ship. If you want fast you go with jet and then truck for the last mile. Airship would be cheaper than air, but noticeably slower, so it basically has to compete with truck on price. Can it do that? Maybe, I have no idea.
