In the sci-fi novel 'Friday', Robert Heinlein writes about a physicist named Daniel Shipstone who realised that 'the problem was not a shortage of energy but lay in the transporting of energy. Energy is everywhere—in sunlight, in wind, in mountain streams, in temperature gradients of all sorts wherever found, in coal, in fossil oil, in radioactive ores, in green growing things. Especially in ocean depths and in outer space energy is free for the taking in amounts lavish beyond all human comprehension.'
In the story, Shipstone quits his job, retreats to his basement and invents a technology that packs 'more kilowatt-hours into a smaller space and a smaller mass than any other engineer had ever dreamed of. To call it an "improved storage battery" (as some early accounts did) is like calling an H-bomb an "improved firecracker."'
Like Ward and Musk [1], Shipstone eschews patenting his new technology in order to deny others the opportunity to steal it (or tie him up in court cases) and instead begins manufacturing the devices (eponymously named "Shipstones") which end up becoming ubiquitous, powering everything from flashlights and automobiles, to households and ocean-going ships. The company he founds becomes the largest and most powerful industrial conglomerate in the galaxy and the method of manufacturing Shipstones remains a closely-held secret.
Elon Musk is by no means the first person to get that realization.
As a theme only things that can be easily reproduced by looking at the very physical nature are patented. If something is easy to reproduce by just looking at the idea or invention itself, that is the kind of thing that is commonly patented. Why else do you think the patent ecosystem if full of crappiest and most obvious patents possible.
It hardly makes any sense to patent some thing that is genuinely difficult to figure out otherwise.
You don't even need a scientific breakthrough or difficult bit of engineering to successfully use that strategy. Coca-Cola is one of the more famous cases of a company that chose to keep its "invention" secret rather than disclose it with patent filings. It was common at the time to patent the formulations of "patent medicines", and the 1890s version of Coke was indeed patented, but later formulations were deliberately not patented, in order to keep them secret.
