To jail people that can't be punished by the server rules by commiting crimes insidfe the town borders e.x. Griefing inside plots(some people claim a plot and destroy the previous house and let it be blank or just go around claiming random plots and this gives the assistants and me more work, stealing or killing a fellow townmember inside the territory or outside it, being disrespectful against town staff, being annoying,...
Town jail is pretty useful, before this feature there was only 1 system : kick people from town when they broke town rules, with the jail you can give members a second chance or if it is needed (when they grief like a lot,and I know this can be prevented by claiming all plots and changing all perms, but some plots are needed to have build/destroy perm on to kill mobs, you can still kick from the town. )