To begin with, I don't think nutaku is the one closing games, but their devs. Ofc, they can decide on removing a game themselves once their contract is over, but I'd say the devs shutting down the game if it's not profitable enough is more likely. Other reasons could be ceasing the whole project or just being discontent with nutaku for some reason. And to answer the question.. surprises, there: game bringing in money is necessary for its survival.
I don't know much of the Aegis case, as I only ever played & cared for KHP. I only read 2nd & even worse 3rd hand information on it, so I can't really say anything on that.