It's to give Kurt something to do on television without taking any bumps. When it first started, it was meant to end with Angle getting challenged by Daniel Puder, playing off of what happened in TE. However, with that idea scrapped, I'm guessing they are keeping it going both due to them not wanting Angle to take any bumps that he absolutely doesn't have to, and because they either don't know how to end it, or are waiting for Smackdown to be held in the hometown of whomever it is they have picked to be the one to end it.
If Angle's neck is that fucked then he shouldn't be on TV in a wrestling role. It's not like his "Angle Invitationals" are even entertaining. It's no more entertianing or of any value than Steve Austin coming out on Raw and beating the crap out of mid-card heels. The only one of any worth was his match with Marty Jannetty (if it is considered one). The should have stopped the thing before Wrestlemania and be done with it.