that every time I've bought a knife, it's come with at least a serviceable, if not a great, edge, but every time I've bought a hatchet/axe the edge made my butter knives look sharp?
I suspect that the quality of the axe plays a role in how well the primary edge is ground and finished. You'll probably have better luck is with a Gransfors Bruks axe or hatchet. They're pretty much the standard.
Given that, if you're going to use an axe or hatchet, you need to know how to maintain it and its edge, or it will bounce when you want it to bite wood. They're soft compared to a knife blade to minimize brittleness.
Given that, if you're going to use an axe or hatchet, you need to know how to maintain it and its edge, or it will bounce when you want it to bite wood.