The argument is that they're more efficient than the alternatives:

> People being defrauded, injured, poisoned, and dying must be much more efficient

> I'm sure an inability to trust the safety, quality, and accuracy of the things one buys wouldn't have any negative effect at all on a market.

And that private business is not an alternative, having given rise to the need for such an agency in the first place and a demonstrated inability to oversee, audit, or classify honestly:

> The illustrious and unbesmirched track record of the worlds major auditing, accountancy, and credit firms has demonstrated beyond doubt that private enterprise can truly be trusted to handle these matters in a manner that puts society's needs at the forefront.

That's not to say that the public agencies responsible couldn't be improved but the idea that privatisation of these matters leads to increased efficiency is farcical.