If you were worrying about gas tank size, the energy density of gasoline would be a worthy issue. However, it takes misreading the meaning of this specific measure to mistake this as a fuel quality. This gets to the size of battery required to offer a specific number of watt hours of energy. Lithium Ion batteries have revolutionized device design by the energy densities, Small Battery Sizes, available.
My Apple AirPods are ridiculously small because the battery that powers them is insanely small. But, my first pair died in two years because of cycle life. I loved them to death. So everything works but you have to break them to fix the battery. Suck!
Unless there is battery technology that they are withholding, they can only fit so many electrons in batteries.
It still is an issue, even with batteries.