They made it without the TU because some people did like the game without changes. If they made the game completely TU, There would be some unhappy players. And if you do want TU, play Squad Slayer. Squad Slayer has it. And it would get boring if the game had the same thing like Halo 3, multiple times, yeah players would want something new.
Also, the beta was to let Halo players have a small taste of some of the features in this game before it was released. It was a great idea from them.