I've read this as the explanation multiple times, but I think there's an even more obvious explanation: people that go into debt, never miss repayments, and nev

I've read this as the explanation multiple times, but I think there's an even more obvious explanation: people that go into debt, never miss repayments, and never pay it off are more likely to continue paying their debt off on time than somebody who never takes on or retains debt. As but one component to this a person who never takes on debt has, tautologically, managed to live a life without any need of debt. That implies he would have little difficulty continuing to live a life without access to credit. Because of this, he will generally have substantially less concern about his credit rating than a person who depends on credit for their basic livelihood.