Depending on your build, people can see it very differently with or without shaders. For example, turning off shaders on a dark map designed for zombies can make all of them quite easy to spot without any effort. I know you can set visible distance which I assume is the same as draw distance, server side in environmental controls, so why not shaders too?
I'd rather have a consistent environment for everyone in the server for balancing gameplay like I mentioned above and just for everyone to see the same aesthetics. Otherwise I might have half the server seeing what appears to be a terrible build and another half with shaders on that are playing it like it was made to be played. Well now that I've explained my reasoning for wanting this, I need to ask, is it possible in the first place?