So they can keep fooling their readers: "China is even worse! We're winning! Jia Freedumb! Jia Dumbocracy!"
Which is not conducive to the health of their Democracy because if the Americans keep watching the rise and success of Chinese economy despite the doom and gloom prognostications from these institutions, the majority of Americans will be then led to believe and are easily convinced that the ONLY REASON CHINA IS WINNING BECAUSE THEY CHEAT, LIE, STOLE ETC...that's the only plausible explanation they'll be able to surmount and process. After all, their media, public officials, deep state statements, and businesses have told them time and time again that China is losing, lying, stealing, oppressing, stifling dissent, spying on it's own people, genociding their minorities, and the government above all else is pure evil.
The Americans will essentially have a melt down or have their brain short circuited because they can't begin to process two competing and contradicting information.
They're not objectively informed as most of the information they absorb are propaganda. Essentially they have been living in the Matrix and when the inevitable blue pill is swallowed then boom of they go..