I think this answers my question (although I'm not sure how old this link is):
"Compared with Google, which offers services in many languages, including Chinese, Baidu has its limitations in several aspects:
1. Credit usage is not popular in China, delaying the expansion of Baidu's online advertising income sources.
2. Baidu only offers services in Chinese, which, in terms of potential revenues, does not match those from similar services offered in English (by Google).
3. Baidu's ranking moved up soon after the Chinese government blocked access to Google by Internet users in China.
4. Most searches on Baidu are mobile phone ringtones, mp3 songs, emule or bit torrance movies, and/or other downloads that involve intellectual property related issues. Most educated people still use Google (Chinese).
5. Baidu puts as many advertisements as possible on its search results, and sometimes, people have to go to page 5 to see natural search results. This affects the quality of its searches."