Because we like our unobtainium, okay?

Also part of it is, we don’t want to get too complicated here, the stuff only really exists to bypass things and maybe give some interesting abilities (for example, the energy output of the “corroded” stuff is unstable. It could be used to provide pulsed power for things like railguns, or as a sort of electrically-fired fuel for missiles.)

So we stick to things people are familiar with. It doesn’t matter if it’s a superconductive wire composed of nonbarionic matter or not- it’s still going to behave a certain way, and sometimes you can get lost in the weeds explaining it, when really it’s just a handwaive away.

I also don’t like introducing power supplies that my party can exploit for really big booms. They may have, for example, opened a portal inside a neutron star (the portals swap a spherical volume of space. So suddenly they created an unstable mass of neutronium roughly 30m in diameter in some douches fleet yards.)

(In their defense the douchenozzle lost control of a sentient grey goo and it was the only way to keep it from spreading.)(but they did blow up half a solar system. And rendered it unnavigable past its Oort Cloud.)