PPP is used for more than just projects - it is less frequent but vitally important when it is used to stop changes from occurring to a controversial profile. From time to time, some gateway ancestor who isn't within a project area is fought over by genealogists who all believe they are correct in changing it back and forth PPP can prevent changes once a decision has been reached on that profile so that we don't start that argument all over again.
It could be interesting to have an alternate means (something not called "project protection") that is used for these circumstances, but at the moment, this is the tool used for that purpose as well.