It is more that the typical reader and writer would like to assign reasoning behind a stock market move. The sentiment driving the market is somewhat more complicated and aligned to many things, but they prefer to give a form of explanation.
This probably comes from the fact that so many people have an interest in where the market is, probably in a passive manner, and due to their 401k. Saying the market moved up today without a conjecture as to why would leave the average investor highly nervous as to why this happened (especially now, at heightened observation as it has been seen to go down a lot and people are sensitive - historically ups did not need explained as much).
The familiarity with the gross over-simplification of what drives finance will be very apparent to anyone who has done a relatively quantitative job of any sort when asked to explain what they do. You make something up completely simple to stop them asking more questions.
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