As any writer will know they are not the best person to look for any errors or omissions in their work. Read it through certainly pick up some obvious mistakes of course. However being too close to your writing is one of the reasons that book editors exist and of course the same applies to essay writing.
Another aspect of essay writing which can be overlooked is that of presentation. The handwritten essay of previous centuries has largely been consigned to history. This certainly creates a level playing field for all academic writing to be presented neatly and legibly. However not all academic writing skills extend to a good knowledge of one of the standard word processing programs such as Microsoft Word. This is another area for essay services to provide coursework help.
Getting students over this barrier was one of the reasons I put pen to paper four years ago and produced a book called Write That Essay! At that stage I was a senior academic at Auckland University and a university examiner. For nearly 20 years in both course work and examinations I had counselled everyone from 17-year-old newbies to 40-year-old career changers with their essay writing. Often the difference between a student who might achieve a B-Grade and the A-Grade student was just some well-placed advice and direction.