alt Hacker NewsOne possible reason (not the GP so I don't know if this is theirs) is that there's a finite amount of helium available, so using it for this sort of use case depletes it for others.
Personally I think a hydrogen version would be hilarious but others might disagree...
I was about to argue that surely the consumption of helium in balloons must be tiny compared to industrial use, but apparently it makes up 5-10% of all helium consumption? That is a magnitude more than I thought, and certainly nothing to ignore for a finite and irreplaceable resource that we need for stuff like MRI machines.