Quote From bongmaster5000:
I don't see how it could possibly be in your supervisor's interest to drag things out and increase the risk of your failing to submit. If anything, s/he'll want you off her/his hands ASAP.
You would think this would be true but surprisingly it does happen.
It assumes that all supervisors are functioning human beings.
I have seen a supervisor deliberately engage in tactics such as this to screw over more than one student. If the relationship has broken down and the supervisor is a right bastard (plenty of them out there), it is no skin off their nose to keep you waiting and in fact it can amuse them to know how desperate you are for a sign off. It's a power thing.
Pissing off your supervisor (regardless of who is to blame) can be truly disastrous.