Whether "oral rehydration therapy" is copyrightable is beside the point. That aside by the author doesn't weaken his main claim. There are no taxes on copyright

Whether "oral rehydration therapy" is copyrightable is beside the point. That aside by the author doesn't weaken his main claim. There are no taxes on copyrights. Yet, my company has to pay taxes on all its other assets. Why shouldn't copyright be treated the same way?