I suspect the biggest reason for not having a path between the two is security.
Have you seen the route into AK? I've not been all around AK, but I have been backstage. It appears AK has clear cut perimeter, several layers of fences and berms, and the main access has those steel barriers that come out of the roadway.
My understanding is it's because they have so many exotic animals. Apparently, zoos have huge problems with people trying to steal animals.
johno