If you operate from the mindset that nix is always responsible for all of the kernel and all of userland, none are unreasonable.
The moment you try to live in a world where nix isn't controlling the kernel, most of those packages are unreasonable. Several provide both a kernel module and userspace tools. Wireguard, VirtualBox, OpenAFS are prime examples that jump out at me. It's totally reasonable to wish to install the userland portion of any of these packages without adding a kernel you cant even use to your system image.
My personal preference would be to see such packages split, with the kernel module package treated as an optional dependency for the userland package. Then the kmod can drag in the kernel and headers only when needed.