The selling point is that there's enough uncertainty and complexity in the process that many (most?) people won't successfully avoid charges for re-buying music

The selling point is that there's enough uncertainty and complexity in the process that many (most?) people won't successfully avoid charges for re-buying music. The icing is that the mere existence of the complex, uncertain process insulates record companies from accusations that they're forcing people to re-buy music (as with the transition to CDs). Re-buying just happens to be the much more convenient option.