Well, it's kinda like say you have University A and University B receiving funding. University A does some research that B wants to use, so B pays A for access. It's just shuffling taxpayer's money around between two different budgets. It never occurred to them that actual taxpayers - i.e. us - would also want to have access. So there needs to be a way to give that access, yet still preserve the cross-subsidy model between publicly funded institutions.