The point is not whether someone could create a registry infrastructure. It’s that they have a hard time getting people to care about it.
I don’t know what percentage of the market cares about the registry, but I personally believe that the grading of high condition commons is driven almost completely by the registry, and has made PSA a boat load of money over the years. That is what is currently suffering from high grading prices. It just isn’t financially viable to pay $50/card to grade 1972 commons. The entire business model of 4 Sharp Corners has been ravaged by these circumstances.
And I realize lots of people only want to grade stuff to sell. But there has to be someone to buy it, and a lot of these buyers are either into the registry, or have typical collector OCD and want all their cards to be graded by the same service.