Because that's good writing. Because an ending like that to a story like that separates good writers from amateur ones. There's no doubt in my mind that TLOU was written to be just one game. There's no room for a sequel. The decision to make one if purely a financial one. No integrity.

And of course I want to know what happens. Everyone does. The ending was designed to make you want to know what happens. The exercise in good writing becomes having the restraint to not tell you. It would be like writing a sequel to Inseption, so you can find out if he's not still dreaming. That's like Aonuma making a sequel to Makora's Mask so you can find out who the Mask Salesman, the Fierce Deity, Termina, and Majora really are. If you can't understand why that's bad, and moreso slimy, writing, then just end I'll just end this discussion here.

What if The Last of Us 2 is to TLOU what Uncharted 2 was to Uncharted 1? :D

I disagree.  Having played the game, it is obvious that even though Joels story is the adhesive, the last of us is a game about people in different situations dealing with the world they live in.   TLOU is the story of Joels survivin' in that world.  All other charachter have their own unique stories but ultimately everyone is living in a world ravaged by the fungus.   One of the great parts of the story is that you could tell that everyone Joel encounterd had a unique story.  The DLC dives into this and lets us explore Ellie's deeper story.   And that was just one character. 

Joels story is the adhesive that holds all of these complex backgrounds together, but each story in itself is very compelling.  Even David's story... or rather especially David's.  Also Marlene's story and Tess; not to mention Tommy and his family... heck even Ish could get a whole game.

*heads explodes*

What? No it isn't. It most definitely is only about Joel, and to a lesser extent, Ellie. It's not about Joel surviving anything. It's about Joel dealing with the loss of his daughter. That's it. Of course they're are others living in that world. It would be inauthentic story telling to not flesh out those characters as they interact with him. Every good story with supporting characters does this. That doesn't somehow make the setting more important. It merely makes the setting more credible. If the setting was WW2 Germany instead of a zombie apocolypse, the characters would be just as fleshed out. Not of that makes a sequel more credible.

We're in a thread about a pretty much already confirmed sequel to the last of us, meaning the people who made the last of us already decided to make a sequel. That's proof, if it wasn't proven already based on the ending, that there is room for a sequel. You claim that making a sequel is sloppy writing, that must mean that you know more about writing than the creators themselves.

lol The Last of Us Remastered 2.5 million probably much higher by now, Infamous 2 million, Driveclub on it's way to 2 million, LittleBigPlanet 3 on it's way to 1 million, Killzone SF, despite how bad it was, sold 2 million, Knack even got 1.25 million. come on now man, i know you love xbox but be real here. i get 15 million may seem overly optimistic but the last of us is a 10+ million seller already.