Essays are by far the easiest to cheat on. Have a parent, older sibling, professional writer write your essay and you look stellar. It happens all the time.
I've talked to a number of people whose kids "came up with the concept" for the essay, and then others got to work on it. How is that representative of the student's quality? It's not.
The fact that essays carry any real weight in the admissions process is silly. Look passed the 4 years of HS performance and then entrance exams, but consider a few paragraphs that someone else writes. Makes perfect sense.