This plugin prevents players from glitching out of the built in Minecraft worldborder. Unfortunately players have been able to use exploits to escape the built in Minecraft worldborder, such as by using boats.
The worldborder is important for server administrators to prevent unnecessary chunk generation, which can drastically reduce server performance, or in other cases to prevent unintended game mechanics - some protection plugin mechanics assume that the worldborder's proper functionality.
For example, on servers utilizing the Bastion and Citadel plugin, escaping the worldborder can be quite problematic because it allows players to 'go around' corner vaults and corner bunkers.