It's not just PR. It's actually really hurting their company. Weaker security means less data can be stored on the iPhone which means less need for it, which means fewer sales.
Companies exist to make money, not to protect our rights. It even crossed my mind that the possibility that NSA et. al. rooted these devices long ago, and that this whole "debate" is just a staged thing to make it appear as though we had any privacy and feigned adherence to the democratic process.
But your point that, as a matter of policy, many organizations will simply not use the product if they know it has backdoors, relates it back to their capitalist motivation and makes any conspiracy less likely.