Writing a long essay instead of a short sentence could be done to:
Cover (one's) ass — TFD
Vulgar Slang To take measures to avoid being held responsible if something goes wrong.
"The police were more interested in covering their asses than in finding the killer."
It's like what Mari-LouA comments:
A person adds a preamble to justify the use of a word because they are afraid of offending someone. They don't want to be accused of generalizing or making sweeping statements.
The method applied could be called:
Circumlocutory — M-W
using or containing more words than necessary to express an idea
the studio's statement that “the film's earnings did not live up to expectations” was a circumlocutory admission that the movie was a flop.
synonyms: circuitous, wordy, diffuse, garrulous, logorrheic, long-winded, pleonasic, prolix, rambling, verbose, windy
Say in a roundabout way — TFD
to imply something without saying it; to say something indirectly; to speak using circumlocution.
"Why don't you say what you mean? Why do you always say something in a roundabout way?"
"What did she mean? Why did she say it in a roundabout way?"
Beat around the bush — TFD
Fig. to avoid answering a question; to stall; to waste time.
"Stop beating around the bush and answer my question."
"Let's stop beating about the bush and discuss this matter."
To speak evasively or misleadingly, or to stall or waste time. To flush pheasants and other birds so they could be shot, British gamekeepers hired beaters who would swing sticks at likely places where the birds might be lurking. Not to go directly to such foliage but to work around it instead gave the impression of wasting time or not trying very hard to raise the birds; hence, beating around the bush.