I'm the last person to defend ratings agencies, but even in a world where ratings agencies were paragons of neutrality and forecasting accuracy one would expect that to be the case simply because those expecting an investment grade rating due purely to a sound business model can lower their borrowing costs by ensuring their bond is rated accurately by at least one of the agencies.

Since the agencies don't rate everything, the best way to ensure that is to pay a fee, so if you're issuing debt without the rating you're sending a pretty strong signal your bond is junk, whether the agency chooses to bother with a "speculative" rating on just how bad it thinks your fundamentals are or not.