Client-side mods are generally very limited in capability. They can't modify the game files. They only provide information available to the player. The thing is that quite a bit is available to the player. There are client mods that can provide darkvision, map reveal, unlimited zooming out, etc. Is Klei responsible for restricting this? These exploits are inaccessible in the base vanilla game so are they exploits?
I would argue that this deserves to be addressed. A player using these kinds of mods can not only ruin their own experience, but others' experiences. When you join a server you are aware of the server mods that are on the server, but not client mods.
Before everyone gets angry because you like to use observer camera to take screenshots of your base or whatever, I'd like to clarify that I'm asking to restrict accessibility client-side. Darkvision, map reveal, and unlimited zoom out will always be an option as server mods, and there's nobody stopping you from using them. If you're stuck in some flawed mindset that client mods don't count as mods but server mods are the source of all evil, too bad for you.