It's a harsh realization that many grad students come to, but unless your grad student is getting some level of results then the advisor will feel his/her grant money isn't going to good use. It's essentially the same thought process a manager goes through when they feel they are paying somebody a salary but that person is not contributing.
This is why independence is so critical and one of the most important traits of a grad student. Time spent telling a student exactly what to do, again, is not always a resource well spent.
Anyways, this is just my perspective on things based on conversations with a couple of my immediate family members who are professors. I went into the normal job market after getting my bachelor's, and I see a lot of parallels between the world of academia and the rest of us. There are different titles and the work is different, but much of the structure and politics are the same.