Helium is a non-renewable resource drilled out of the ground, of which there is a global 'crisis' shortage[1]. Hydrogen is easy to make in vast quantities and cheaper. But more importantly, while they have similar lift capacities on paper (Helium ~90% of Hydrogen), in practice they don't - https://www.airships.net/helium-hydrogen-airships/ has an explanation and calculations.

Hydrogen lift airships set off fully inflated and vent Hydrogen along the way for control of altitude and to stop their lift cells expanding too much as they rise into lower pressure air; Helium is too expensive to vent casually, so they have to start less inflated to protect the lift cells, and other concerns so Helium lift ends up with half the payload carrying capacity, less fuel, shorter flight distances.

And, nb. the deadliest airship disaster was the USS Akron which was was a Helium lift airship which crashed in a storm with 73 deaths and 3 survivors. It's not as simple as Hydrogen = danger, Helium = safe.

[1] https://www.forbes.com/sites/omerawan/2022/11/10/the-helium-...