They use actors for motion capture bro.
Also it looks ugly in HD thats why.
The digitized actors was a total accident.
The digitized actors might have been an accident, but it was a happy one. I'd be more inclined to take the ugly-in-HD argument if I thought the faces in MK9 looked perfect.
Also, it isn't all about necessarily pushing technology to the limits and using every damn thing available. Console makers have been trying to sell people on the Move and Kinect for years, but most people don't care. 3D Dot Game Heroes *intentionally* makes their games look old school and sold just fine. Why? Maximising graphics isn't all there is to something. 3D Dot was a full-price game and sold six times as many units as anticipated
A perfect example is Journey on PSN. A super hit, award-winning, top-selling game that is awesome. Yet, you can't talk to the person you are co-oping with.... Why? The technology obviously exists to allow people to talk in co-op, it would be easy to put in there. Yet, that is just part of the game. It is part of what gives it character. Actually, the game wouldn't be nearly as good if you could talk your co-op partner. What about Angry Birds? Did anyone care that the graphics weren't 1080p? No.
There are plenty of flash, 2D, cartoon looking games that do great. Just saying, sometimes when playing MK9 I'd rather have some choppy, real actor animations a la UMK3 than the super-polished, but still not quite there, graphics we get. Injustice is kind of its own animal, being most of the characters are known for their animated state anyways. MK though, damn, especially with the new consoles coming, I hope they still consider it sometimes. At the very least, if the technology isn't there, then their goal should be to get back to real-life as soon as it does.