The fuel for it is the most common on the planet, if not the universe, requires no special refining

It is true that regular hydrogen (with 1 proton and no neutrons) fuses in the Sun, first to deuterium (2 protons combine into a nucleus that immediately decays a bunch of radiation and becomes a proton and neutron), then another hydrogen proton to create helium-3 (2 protons, 1 neutron), then two helium-3 nuclei fuse to create 2 hydrogen protons and a stable Helium-4 nucleus (2 protons, 2 neutrons).

But nobody on earth is trying to accomplish fusion through that difficult pathway. We don't have the ability to create the pressures and heat to ignite that reaction.

The way all of these fusion projects are trying to achieve are deuterium (1 proton, 1 neutron) plus tritium (1 proton, 2 neutrons), to form Helium-4 (2 protons, 2 neutrons) plus a neutron and a bunch of energy. That is a reaction that human technology can ignite. So all the research goes into this particular reaction.

And for that, tritium is exceedingly rare. We can make it as a byproduct of fission reactors, from lithium.