Because it's not the most important thing in China.
For Chinese, the current topic is economy. We are at different stage of development. The western countries have finished this stage already so they have more time to talk about democracy, freedom, etc. But how can you imaging the people in a country in war (think about Iraq) or of very poor economy talking about democracy or human right? If your life is in danger, who cares about human right? Of course, it is an extreme case and China is not that bad. But what we Chinese want NOW is a better life. Of course, democracy helps to build a better life, but comparing with developing economy, the benefit from democracy is much less. In a sense, democracy and human right is included. When we have a better quality of life, have better education, people start to think about all these kind of stuffs. It is a nice topic, but it is not that attractive to us right now.
And the current situation is that we ARE doing much better, not only in improving our life but also freedom, democracy, etc. Maybe it is not as good as what you have in the western world, but come on, how long does it take for the western countries to build the social system they have now? That takes hundreds of years and China needs time. Also, if you were able to look back at China 30 years ago, you will know how big improvement we made and is making. That's why we know we are now on the right track. That's also why this time Chinese people have such strong resentment to the western median and politicians because they are taking advantage of the sexy topic of human right and what they really want to do is to force China to go on a track that they want but we don't. Whatever they say, I believe we will not change our mind. Rome Empire was not built in one night. We just need more time and economy is the most important now.
Also, I would like to suggest the westerners come to China. Western people really like to talk. But instead of talking, please come and see a REAL China. The freedom and human right are not as bad as you think.
I am doing my Ph.D. degree in the US now and I have been living here for 2 years. I also visited several big cities in Canada 3 years ago. Maybe it's hard to believe, but I don't think the life here is much better than what I had back in China. Many of my friends who came here also have the same feeling as I do and most of us want to go back after finishing our degree. Of course, it is better in a large scope of view, but the difference is not that big and I would think it is mainly in culture rather than the freedom or things like that. In terms of daily life, I cannot feel that I have more human right here even though it is claimed so. So personally, it is not attractive to me.
If you really what to know China and why we think this way, throw away the newspaper, turn off the TV and go on a trip. It may sounds blunt, but I really want to say, if you don't understand China, please don't tell us what we should do. We do what we want and if we really need it , we will definitely do it.