If you found such a material, would you want it in your pocket? Or someone else's pocket, where it could break in an accident?
You are right. They are definitely not ordinary consumer products. However, they might be useful where recharging or exchanging a battery is impossible or associated with serious disadvantages.
For example, in the past cardiac pacemakers had been used with nuclear batteries. However, there is a risk that the pacemaker will be “forgotten” after death, and something that is actually radioactive hazardous waste will be disposed of via crematoria or cemeteries.
Another area of application for nuclear batteries is space exploration.
Or my favorite, Marsilio Ficino. There is a statue to Ficino when you walk into the library. Ficino was hired by Cosimo Medici (the Florentine who invented banking and funded much of the Florentine renaissance) to translate Plato and other esoteric books coming from the fall of Constantinople. He published “De Mysteriis” in 1497, which paraphrases neoplatonic understanding of Gods, Demons, Heroes and Soul — arguing that gods and demons don’t feel — indeed, not even the soul (“the lowest of the divines”) has any part that feels.
(Aside: This idea was actually referenced in “K Pop Demon Hunters,” where they debate whether demons can feel — or are “all feelings”)
It is an old Pythagorean tradition that sensation or consciousness arises out of the interaction of the immaterial soul and the material body. That “three world” idea is echoed by Nobel Laureate Roger Penrose in his book “Road to Reality.” He talks about how the material world produces the world of consciousness which produces the world of ideas (including mathematics), which seems to produce the material world…
In any case, there are many old ideas and nuggets of wisdom that have yet to be mined and discovered— don’t think for a moment that scholars have read all these books! We might need AI for that…
Umberto Eco probably did.