[kobeya]

The main industrial use of helium is in selling cold -- things that need to be done cold are done at liquid nitrogen temperatures. Things that need to be _really_ cold are done at liquid helium temperatures. Think superconducting magnets and MRI scanners. This usage can, should, and usually is recycled. Being a noble gas it doesn't really have much chemical applications per se. However according to wikipedia it is also used in "pressurizing and purging systems, welding, maintenance of controlled atmospheres, and leak detection." These usages are lossy by their very nature.

However helium leaks like almost nothing else. Only hydrogen is worse. It is so small that it is able to leak (slowly) through the crystal lattice structure of metals, ceramics, and other materials used to contain it. So recycling systems can't be made perfect.

And of course, even if recycling systems were perfect, a limited supply means no room for growth.

[CamperBob2]

Actually I'm not sure hydrogen is worse, because it's normally found in diatomic form. What's bigger, a single helium atom or a pair of conjoined hydrogen atoms with their own nuclei?

Hydrogen will leak through porous metals like palladium, but as you say, helium will leak through almost everything.