Liquid hydrogen is impossible to work with at large scales, it causes embrittlement, leaks like crazy, has poor volumetric energy density, requires storage in vacuum-insulated tanks, etc.

Molecular hydrogen does not cause embrittlement (neither gaseous, nor liquid). This is a concern in certain chemical reactions that produce atomic hydrogen, but not in any storage applications.

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It certainly does. The higher the pressure, the worse it gets. And it absolutely applies to storage.

There are companies that sell various technologies for hydrogen-resistant coatings for pipes, for example.