It was definitely true in my high school English classes ~20 years ago that we would get red ink on our papers if we used what were termed "weasel words" like "suggests" and "believe". I have no idea how representative that was, or which direction the trend has been since then. We were also taught to use short, declarative sentences wherever possible, Hemingway being the ultimate example of the "beauty" of economy in language.

It is my understanding that this is a very USA-centric trend in writing, probably being exported along with the rest of the complex basket of American cultural quirks that come along with US-led internationalization (hegemony if you like) since WWII.