Why do chinese resturaunts give those extra white rice ?

I'm not sure what you mean (is it free??), but Chinese meals are typically eaten with a bowl of white rice and several dishes. Do you get them even if you order noodles or fried rice?

To Asian, rice is a basic food, as you must have drink in your meal. You can eat many kinds of dishes, but you must always eat rice in your lunch and dinner. This opinion is like the fact that if you want to write, you must have paper and pen. So, if you eat, you definitely eat rice. You can eat rice with every dishes, except for noodles because noodles is a substitution of rice. An Asian hungry only eat rice with fish sauce or soy sauce if he has few coins left. Rice is cheap and that is another reason Asian restaurants usually offer rice for free as an added value of their service.

The dish is probably meant to be eaten with rice, that's why. Besides, Chinese cuisine has a lot of rice & noodles, so they assume you might need that extra rice :)

rice is yummy