Although the most companies are focused on the resume rather than cover letter. Many applicants who think that the cover letter is not necessary and not attached to the resume. Nevertheless, do remember that there are many companies still use the cover letter as a screening test to the applicants.
As well as everyone knew about a resume. Resume is the standard format of a letter that for apply the job. Nevertheless, resume has a problem about its format that was not flexible and quite fixed. That is why many companies cannot know other details about you as good as it should be. So, cover letter used in conjunction with the resume cover sheet to indicate the intent of the applicant. Thus, It may be called a Cover Letter is an optional features for competitive advantage to other applicant with the same position and similar skills.