So if you disable the option for world PvPers to world PvP you are gonna lose a lot of people.
You don't know how pve servers work then. They don't disable anything. They allow you to choose if you want to do wpvp or not. Do you want it? Flag yourself. You don't? Toggle it off and people can't attack you in contested zones. In pvp servers you simply don't choose, you are just forced.
Furthermore there is a bout 6 guilds currently on alliance side actively recruiting for just world PvP/Premades/Arenas. I have no clue for horde anymore seeing as i haven't been on there a while.
Come on, you see those kind of shouts once in a while, only a fraction of other spammed activities.