I have a Project named "Find agent for YA novel." It's halted with a Waiting For regarding a query I sent to an agent. If that email comes back with a "Yes," I'm going to have a lot of work to do. I want my Projects list to reflect that.
The alternative is to get five replies in a day on various projects, and find your Projects list ballooning overnight to an unmanageable level.
That's what works for me, at least.