Some discoveries founder in the stage of figure out how to go from a science experiment to a process to manufacture actual batteries. Sometimes there are technical or economic issues that prevent commercialization.

Most of the research on this has only started in the last 10 years or so and it does take time to work out the kinks.

Even within the common Lithium-ion batteries, there have been constant improvements but it’s easy to miss the changes over time.

“Eternally five years away? No, batteries are improving under your nose” https://arstechnica.com/science/2021/05/eternally-five-years...