Well, because the way that mesh networks (at least mesh-toplogy networks) function is to route packets to neighbors. Nodes don't blindly and neutrally route packets along; they select specific packets to route to specific neighbors.
On a mesh (at least in OSLR or BATMAN), nodes only route certain packets. They are also free to drop packets for any reason, be they geographical or economic. Nobody can demand that a node perform routing.
I can absolutely imagine a malicious regulator claiming that the law requires every node on a small-town mesh to cart Fox News to the other side of town with just as much priority as packets originating from within the town. And that's not really sustainable for a mesh.