Such "coaching companies" can cause so many problems for visa applicants because they have been known to advise people to no tell the truth about certain aspects in their life (e.g. saying they are married when they are not). This haunts people because they are denied the visa anyway and then if they apply for a spousal visa at a future date, they will be required to show documentation pertaining to something that never happened. Using the example I gave, the applicant would have to provide documentation showing that the marriage they claimed to be in has ended. That would be impossible because it said marriage never was.