I think there's a variety of reasons why a state may choose to not recognize non-resident permits. Don't take any of this as my endorsement of any particular situation. Just my attempt to understand why.

In the case of Delaware, I think it's the specific wording of the law. The quote I found reads...

“The State of Delaware shall give full faith and credit and shall otherwise honor and give full force and effect to all licenses/permits issued to the citizens of other states where those issuing states also give full faith and credit and otherwise honor the licenses issued by the State of Delaware pursuant to this section and where those licenses/permits are issued by authority pursuant to state law and which afford a reasonably similar degree of protection as is provided by licensure in Delaware and publish a list of reciprocal states annually on January 15.”

The way that is written is pretty clear. The law does not just say permits issued by a reciprocity state, but permits issued to citizens of reciprocity states.

I also could understand the reasoning behind a state's decision to not recognize non-resident permits if a Permanent Brady Permit state decides not to recognize the non-resident permits of a non-Permanent Brady Permit state. Not sure if that's actually the case anywhere.

I think a lot of this has to do with the fear that criminals may slip through the cracks somehow. It's not like the sharing of criminal information between the states is perfect. They may fear that someone with a non-resident permit has some problem in their home state that may prevent them from obtaining a resident permit. The fact that there may not be any evidence that has actually happened is irrelevant to them. They have as much trouble figuring out all the minutiae of this situation as we do. If they suspect that it's just a loophole, they'll close it.

If the states would get together and standardize their procedures to some degree then it might help clear up the confusion. National Reciprocity by negotiation between the States.

I don't see how National Reciprocity is ever going to happen. They may pass a law but I expect it to be over-turned at the Supreme Court when challenged by one of the states that is sure to oppose it on States rights grounds. But I've been wrong before.

The only way I see National Reciprocity would work on the Federal level is if the Federal Government issued the permits.

I'm leery of supporting anything that erodes State's rights. Sometimes you have to take a stand for what's right, even when it's inconvenient. Especially when it's inconvenient. The Law of Unintended Consequences always worries me.